Without assistance from his PAK, Zim is forced to rely on the atmosphere for oxygen. The row of holes along his abdomen are missing on his new human body. The trachea that normally runs through his thorax is in the wrong place, shallow and incomplete beneath his chin. What has Dib done to him?

Zim screeches. "I can't breathe!"

Dib's visual field feels like a Picasso painting. He can see himself across the room, but blurrier; Zim gasping for air from inside his body.

"Use your lungs, stupid!" Dib screams. His own voice is foreign; his tongue thrashes like a stuck snake.

"I'm dying!" Zim insists, even as he begins drawing in air through his nose.

Eventually, Zim collapses. Dib isn't sure whether or not he's alive until he's peering at his face from two feet away. Dib's new eyes don't adjust to light like they used to. Zim's pupils dilate and he grabs Dib by the throat.

"What did you do?" Zim screeches. "I demand my body back!" Dib knocks the glasses from Zim's face. "Give me back my body!"

Zim wrestles Dib to the ground with minimal effort. There's a six inch height disparity between them, easy. Zim's amber eyes light up at the realization and he digs his fingernails into Dib's green flesh.

"Who's the tallest now, Dib?" he says venomously.

Zim towers over him from within Dib's body, but his movements are clumsy and uncoordinated. When his knee slips Dib throws all his weight forward and Zim crashes into a computer monitor.

"Still me, stupid!"

The punch misses; Dib's arms are shorter now. He tries again but Zim grabs him by the antennae, knocking his head against the counter. When the room tips Zim laughs.

"Computer! Dispose of the filthy trespasser!"

Dib awakens on the floor. The blood on his forehead has dried and the wound has already healed. Zim's base is empty. Dib can hear heavy footfalls and Gir's shrill voice echoing through the floor.

"Computer," Dib says cautiously. "Where is Dib?"

"My head's not big!"

Outside on the front lawn Zim struggles to move. There's a first degree burn on his calf from where the laser caught him, cropping the last few inches of Dib's trench coat in a clean line. The interchange with the garden gnomes leaves his peachy flesh marred; blotted with purple and blue like a galaxy photograph.

Zim flinches at the appearance of his own flesh. Dib puffs out his chest and steps into the sunlight. The scream that follows is not his own. Zim pushes himself onto his elbows for a better pointing range.

"Look!" Zim wails. "An alien!"

When pedestrians turn to the commotion Dib throws his arms over his head.

"You've got it all wrong! I'm not the alien, he is!"

The fantasies Dib entertains have come back to haunt him: a dissection from a different point of view, a scalpel below his green alien belly.

"Me? An alien?" Zim waves him off. "I'm just the local Dib-headed crazy boy."

A heavyset woman with curlers in her hair nods in agreement. "He does have weird eyes," says her son. "And green skin," says another. "And that is Dib," concedes the third.

Dib sputters, backpedaling into Zim's house. "I have cataracts!" he screams. "And a skin condition!"

The door slams shut while Zim laughs from the front lawn. Two hours tinkering with alien technology proves no more effective than the work he's done already on Tak's ship. Aside from Zim's dubious security network, Irken software is indistinguishable from common trojans. Dib can feel his body draining as he works, a pit in his stomach like hunger but darker.

Every attempt to activate Zim's PAK has proven unsuccessful so far. He concedes to ask Zim for help and finds him unconscious on the front lawn; the garden gnomes drag him inside. Dib's first mistake is not restraining him. Even as a human, pain alone is not enough to incapacitate him.

"Wait!" Dib begs before Zim pounces. "I need your help," he admits.

The next step, apparently, involves disrobing. Zim pulls off the trench coat and then at the smiley face t-shirt.

"What's wrong with your horrible earth skin?" Zim tosses the clothes to the floor and starts with the pants zipper. "Is it always this hot?"

It feels like a competition. Dib tears at the standard issue Irken uniform. He's never worn a dress before but he imagines it's kind of like this: open and breezy but impossible to pull over his shoulders.

"This is for science!" Dib cries, undeterred.

A shoe narrowly misses Dib's head as he finally removes the fuschia tunic. His sternum is arranged differently and his chest is smooth without nipples or a navel. Zim shrieks at the discovery of both.

"How many holes do you have in this thing?"

The repulsion is unanimous; Dib half expects vomit. Zim trips out of his pants while Dib unlaces his boots. There's an Irken insignia on his underwear that he's almost too afraid to touch. Along each of Dib's sides is a row of holes. Dib covers a few with his fingers and takes in half as much air.

Dib struggles to speak, breathless. "You're one to talk!"

The last of Dib's clothes disappear, but Zim is more interested in his own biology. The nubs on his chest make his muscles contract when he touches them. Zim's attention shifts. There's something leaking onto the ground next to Dib's three toed foot. Dib looks down at his unfamiliar anatomy and Zim laughs. He's smooth and solid between his legs like a Barbie doll.

Zim smirks. "Is that for science too, Dib?"

Dib shoves a hand between his thighs and when he draws it back his fingers are sticky. He shakes his head.

"This is…" Dib falters. "This is your body!"

Zim reaches the final layer of clothing and trips out of an old pair of y-fronts. Dib has never felt more dysphoric, watching Zim carefully inspect his flaccid penis. He lifts it carefully between his forefinger and thumb. Only mammals walk around with their sex organs flopping about in the open.

"Humans are disgusting," he informs Dib with a shudder.

When Zim pulls back the skin and his penis twitches he jerks his hand away like he's been burned. The whole calamity is almost worth it to see Zim's face twist in fear. Except, really, it's his own face.

"What was that?" Zim demands, eyebrows shooting to the top of his forehead.

Dib swallows. He'd laugh if he wasn't in the same boat. "Reproduction," he admits, hunching his shoulders.

"Your body is preparing to make grubby human larvae now?"

Dib's voice rises, cracked. "You've probably been waiting to probe me since you landed!"

Zim sneers. "You'd like that, wouldn't you Dib?"

Dib watches in horror as Zim palms his cock. The taste of triumph is almost too sweet. Humans are easier than most species, primal and soft.

Dib stomps his foot. "Stop touching my body!"

Zim bears his teeth, close to retching. "Foolish human! Do you think I want to touch your repulsive meat parcel?" He pulls a silver bucket from a pink cabinet that resembles a porthole. "We must provide genetic material to complete the antidote!"

A moment of silence for Dib's filthy earth brain.

"You're telling me the only way I can get back into my body is some kind of…" Dib gesticulates with his hands while he searches for the right words. "Alien reacharound?"

Zim folds his human hands together. "Yes."

Technically, it's closer to mutual masturbation. Slowly, Dib snakes a hand between his legs. He only has three fingers and they bend in different places.

"I'm not going to jerk you off," Dib decides. "I don't even know how to work this thing!"

"Insolent fool!" Zim spits, yanking Dib closer by the arm. "Even smeets can empty their primordial spooge sacks!"

Dib stumbles back a few paces and trips over a boot. "Leave me alone!" The thumbprint on his wrist fades when he pulls his hand away. "I'll do it myself!"

Zim scoffs. "Good luck mastering my superior Irken biology."

Dib's antennas flatten. "I can master your stupid alien biology all night long!" He steps forward and pokes Zim's chest. "Without your help!"

Predictably, the opening between Dib's legs can barely fit his finger. Even that much width causes incredible discomfort.

"Idiot!" Zim thrusts a bucket into his chest and Dib shoves it back with more force. "At least try to aim for the transgenetic modulator!"

Zim points to a large piece of Irken technology. It looks like a washer-dryer with too many buttons and a purple electric current. Zim throws the bucket at Dib's head, but misses.

Dib glares. "It's your fault we're in this mess in the first place!"

"My fault?" Zim's voice is comedically high, but his eyes flare dangerously. "If you hadn't used your icky poop hands to break into my precious base then none of this would have happened, filthy human stink boy!"

Before Zim can continue his monologue, Dib attacks him. He pulls Zim by his ponytail and digs his knee into his back. Zim twists around and grabs Dib by the antennae in retaliation. He shrieks as something behind his slit wiggles at the unwanted attention. Dib socks him the face to compensate, reeling away in repulsion when Zim's cock stiffens beneath him.

With two feet between them, Dib can see more clearly. "Is this...making you hard?"

"Hard?" Zim snorts. "This pathetic body is nothing but flab and squish organs!" He pokes at the testicles hanging behind his penis. "There is nothing hardened about this disgusting meat cage."

Dib sighs; his head is starting to hurt. He curls his fingers around the steel rim of the bucket and stands up. His knees feel like jello.

"Let's just get this over with."

Loathe to admit the scuffle with Zim did anything for his libido, he turns away, bucket secured between his ankles. Brows furrowed in determination, he jams a finger between his legs again.

The girlish shriek that follows has Zim howling with laughter. "Nice one, Dib-stink!"

Dib winces as he pulls his finger away; dry. "I don't see you doing any better, Zim!"

"Stupid, stinking human..." Zim shakes his head, hands at his hips. "I could master your primitive mammalian meat stick with my eyes tied behind my back."

Zim reaches for his penis, still at half mast. Dib watches in horror as it rises to full attention in his palm. For Zim, the taste of triumph is almost too sweet.

He smirks when he catches Dib staring. "Watch Zim as he schools you on your own obscene anatomy!"

Dib folds his arms, eyeing him skeptically. Zim's confidence falters when he squeezes too hard. He smothers the scream, but the tension tells the rest of the story. It softens in his hand, and Dib points a finger.

"Hah!" Dib gloats. "Not so easy, is it Zim?"

They stare at each other, then their corresponding genitalia. Dib almost asks him for help. Instead he turns to face the oversized monitor behind the throne of a desk chair.

"Uh, computer? Give me all the information you have on Irken mating practices."

Zim curls his fists. "Ignore his command! Obey Zim at once! Listen only to me!"

"Um." The silence that follows is stilted. "This is kind of awkward."

Dib throws his hands in the air. "Just tell me already!"

"Okaaay…" The computer clears its metaphorical throat. "Processing."

Zim's face turns red before the computer begins its explanation.

"Coitus between two Irkens begins in the oral cavity and ends in the copulatory pouch. Each partner inserts the proboscis behind the pleasure plate, into the coital orifice, located on the sixth thoracic segment."

Without a diagram the rest is too abstract to be applicable. Dib peers at his stomach, pawing at the place below where his bellybutton should be. No umbilical cord, then. The explanation offers no solution for his problem.

"Ejaculation occurs after the proboscis entwines with the internal phallus, and the primordial spooge sack releases."

Zim pulls a heavy cord from the outlet behind his desk and the screen goes black; the room is quiet. His face resembles a beet but his cock is rigid against his thigh. His chest is heaving.

"This is over, Dib-beast." Zim narrows his eyes and when he steps forward Dib steps back without thinking. "I'm finished waiting around for your primate intellect to catch up."

He shoves Dib against the control panel and drops to the floor. Dib gapes as he clutches the edge of the desk. Zim digs his fingernails into Dib's kneecaps and forces his legs apart.

"Get a good look, Dib-stink. This is the only time you'll ever see a mighty Irken invader on his knees."

He slides his hand between Dib's thighs and leans forward. Dib remains frozen, too afraid to set Zim off this close to genitalia he doesn't know how to operate.

Dib swallows a sound as his nerve endings light up. "Are you gonna...eat me out?"

There's a glint in Zim's eyes when he smiles. "Oh, I'm going to do much worse than eat you."

Very carefully Zim brushes his fingers below where his hips meet in the middle. Dib still flinches at the contact. With surprising delicacy, Zim teases the place below the hardened plate on his abdomen. His thumbs press at the smooth disk until the skin underneath parts along an invisible seam. This is it, Gaz is going to tell him later, he's finally crossed the line.

Zim curls his index finger and slides his knuckle against Dib's slit. When he makes noise it's more gratifying than he expected. He sniggers, pulling away.

"Enjoying yourself, worm?"

Zim laughs when Dib stuffs a fist in his mouth to silence the sound, but it's of no use. Two tones: not quite a buzz but not yet a chirrup. It sounds like a high-speed drill bit piercing straight through steel without lubricant. Something in Dib's chest contracts, shifting the muscles around his rib cage with a clicking noise. The sound softens to a low hum as Zim leans forward to kiss his genitalia.

"Is this normal?" Dib asks when he finally catches his breath. He presses his palms to the rumble in his chest as his legs begin to tremble. "To sound like some kind of...cricket or cicada?"

"If you mean the Calling Song, it's just an outdated biological function Irken scientists are already working to remove."

When Zim opens his mouth against Dib's hole his antennae perk forward, wavering in the air. The chirping redoubles, rising in pitch as Zim teases him open with his tongue. Only Zim could look this smug from on the floor. Dib's hands pause midway above his head when Zim throws him a menacing look.

"Try it, Dib-pig, and I'll tear off your arms."

Zim's human tongue is only half as long and nowhere near as flexible. It only folds in two places, and it doesn't come close to reaching the copulatory pouch, but Zim is an innovator. He makes do with his inferior human anatomy. He clutches Dib's hips for a better angle, eyes on the ceiling as he pulls Dib forward onto his face.

Sweet success. Dib's palms press into the keyboard as Zim finds Dib's entrance, worming his slippery tongue into the narrow canal. Vibrations begin from the ridges on either side of Dib's torso and reverberate through his tymbal as the muscles collapse and inflate. He trills and his thighs quake.

"Zim!"

The sound of his own name spurs his pink sex rod into action. It sticks where genetic fluid has begun leaking against Zim's belly. Dib's hands grapple for leverage as Zim steers his tongue the rest of the way inside him. His antennae twitch as Zim wiggles his tongue and something unfurls and reaches out in return.

"No way! Stop!" His legs are trembling. "Whatever that was-no more, Zim!" Dib scrabbles at the slick surface of the desk and tries to pull his knees up.

"Stupid mammal," Zim says with a wave of his hand. "That is merely the bedworm!"

The explanation does little to console him. Zim pushes Dib back until the edge of the counter cuts into his skin. When Dib squirms in his hands Zim feels it in his gut, then his groin. Zim buries his face between Dib's legs and seals his mouth around the sloppy hole. With minimal coaxing the bedworm reemerges, tentative as Zim licks each ridge in full.

"I'm close, gonna-nghn!"

The shrill chirping falls and then rises, reaching a crescendo as Dib begins to convulse. Zim twists his tongue deeper, curling around the pulsating phallus as it responds in kind. Dib's fingertips brush his shoulders, but Zim let's it slide. He pulls back and licks his lips before the spooge sack releases, thrusting the bucket between Dib's legs. The muscles contract and release; rhythmic. Less than a teaspoon of pink spunk dribbles into the pail as Dib spasms.

When Dib can breathe again, he has the nerve to snark. "Like the taste of yourself, Zim?"

Zim's teeth lock together in a nasty grin as he holds the bucket close. "Ready to find out?"

The thought makes him feel sick. Dib heaves himself upright and steadies his gait. Then he shoves Zim into the transgenetic modulator. Zim stumbles but swiftly turns to face him, bucket pressed to his chest, erection flagging.

Dib sighs. "Just turn around and hold the bucket before you accidentally yank my dick off!"

Zim narrows his eyes. "An invader never turns his back to an enemy!"

"Well I can't jerk you off from the front!" Zim doesn't budge until Dib goads him. "Scared of a little handjob, Zim?"

It's awkward now that Zim is taller but Dib manages away. His own penis feels foreign in his smaller hand, bigger than it really is. His thumb doesn't reach his forefinger but his hold is good enough that Zim's cock jumps as he encloses it. Dib pulls back before things get too messy and licks his palm.

Zim tries to turn his head, mystified as the human works the oversized sex organ jutting out from between his legs. Dib pulls his hand over the shaft from top to bottom and Zim's toes curl against the floor. He clenches the pail until his knuckles turn red.

"Why is your hand-" Zim loses his voice behind a squeak as Dib pumps his cock.

He watches as Dib twists his wrist on an upward stroke, pulling back an inch of extra skin before reaching the base. He presses his thumb to the bulbous head and squeezes. The sensation stretches to his heels and back. He tries to swallow a grunt of desperation and ends up gasping for air. What's the deal with lungs, anyway?

His knees buckle and Dib laughs against his shoulder. "Geeze Zim, did you do any research on humans at all?"

His cock throbs as Dib settles into a rhythm. He uses his other hand to tease the skin behind Zim's testicles. Zim shudders, tilting his pelvis for more friction until he's sliding between Dib's wet fist. When Dib tightens his grip and speeds up Zim's hips grind to a halt.

"Hey alien, ready to cum?"

When Zim falters Dib braces his weight with an arm around his waist. Despite Dib's shorter height, his own strength surprises him. The bucket rattles in Zim's hands as Dib milks him, semen splashing against the tin.

The whir of machinery startles them. Dib almost forgot why they were doing this. Zim tips the container and watches the pale pink drain into the reservoir. Going back into his own body feels like being ripped apart and stitched back together.

"You did it," Dib confesses.

Zim grins. "I'm an unstoppable death machine, you know."

"Now be gone with you! I've had enough of your nonsense from your smelly mouth filled with... corn!"

"But I haven't been eating corn..."

"Liar!"

The gnomes come for Dib after that. At least things are back to normal.