A/N: Wow, sorry for taking so long to put this last part up! Things have been pretty crazy lately. Anyway, if you're reading this, thank you so much and I love you. Also, I'm currently writing another Perryshmirtz story, so I hope you'll read that too when it's up! ;)

Perry is worried.

His nemesis has been acting weird around him for a week now. He won't let the platypus see the contents of his closets, which he is usually only too eager to blather on about; he has a day in the middle of June circled in red on his calendar that he refuses to explain; and worst of all, he's stopped inviting Perry over outside of work. It's become something of a habit for them now, for Perry to visit even on days off and after thwartings: Sometimes he stays for dinner on weekends when Vanessa is there, sometimes he helps Heinz rearrange his furniture "to ease the flow of evil chi," and sometimes they just sit on the couch and watch soaps (which they both deny having cried during, thank you). Heinz usually makes cake. He's made a dozen different kinds, and they're all amazing.

When the evil scientist says nothing on Tuesday about Perry and him catching their usual soap tomorrow, the platypus can't help but feel a little heartbroken.

The following morning, Monogram sends him out early. "Dr. D. has acquired an industrial-sized mixer, 50 eggs, a half a ton of flour, and an entire orchard's worth of cherries, among other things," he'd said seriously. "We don't know what he's up to, but it sounds messy." Perry salutes and jetpacks away.

His webbed feet touch down lightly on the balcony of Doofenshmirtz Evil Incorporated shortly afterward. Heinz's invention of the day is huge, and covered by an enormous white tarp. He's just about to look for self-destruct buttons when suddenly the evil scientist strolls out onto the balcony, Norm the Giant Robot Man behind him.

"Perry the Platypus!" the doctor greets. He presses a small remote in his hand. "Why don't you sit down and stay awhile!" he cackles as a high chair rises out of the floor and belts the platypus in firmly. Perry struggles against the belt, but his paws are pinned by his sides and no matter how he wriggles he can't break free. He has tons of ways to get out of this, of course, but he figures he'll be polite and let his nemesis do his evil monologue first. He glares at Doofenshmirtz, hoping it will cue him.

"It took quite a while and quite a bit of planning and a LOT of wasted eggs," Heinz says, and then spitefully aside, "Norm."

"I'm sorry, sir!" Norm says cheerfully. "I thought you wanted it crunchy!"

"WHERE DID YOU EVER GET THAT IDEA, YOU INCOMPETENT—" Heinz takes a deep breath and reins in his outburst. "Never mind, it doesn't matter. What matters is that you, Perry the Platypus, are here to witness the power of my newest creation! BEHOLD—" He rips the tarp off the massive object. "The Celebrate-inator!" Perry's mouth falls open in awe and his eyes go wide. Before him is a gigantic, incredible, impossible—

"I know, I know, it just looks like an enormous birthday cake," Heinz says, and after a short pause, "That's because it is." He clears his throat and runs a hand through his unruly brown hair, suddenly awkward. "Um, I'm just gonna cut to the chase here: Happy Birthday, Perry the Platypus." Another pause. "This is your cake," he adds, gesturing unnecessarily to the un-miss-able confection.

Perry gapes. After a few seconds his eyes start to feel dry, so he blinks them rapidly. Birthday cake? His? His birthday cake? How had the doctor known about Perry's birthday? Even Perry had forgotten Perry's birthday!

"I had to call Monobrow to find out when your birthday was, you know," his nemesis says as if reading Perry's thoughts, walking closer to Perry's high chair. "He didn't know it either! He told me to ask that strange kid, what's his name, Cal or something. And that guy did know!" There is something like pride in his voice as he tells the platypus everything he'd done to accomplish this task. "Who knows how he knew? Then, I had to discover your favorite kind of cake! Chocolate. White. Angel. Devil. Over the past few months, I've made them all, but none of them captivated you quite so much as this one: the Black Forest cake!" He takes a moment to do his evil laugh before continuing, as if making a platypus a giant birthday cake were actually an insidious plot. "Of course, the hardest part was hiding the fact that I had a massive mixing bowl hidden in my closet. I had to use Norm's closet since it was the only one big enough."

"I slept on the floor next to the air vents!" Norm adds enthusiastically. "It was very lonely and uncomfortable!"

"You're a robot, Norm, you don't sleep!" Heinz says impatiently before turning back to Perry. "So, Perry the Platypus? What do you think?" He wrings his hands together, as if anxious about his nemesis's reaction.

He'd been planning this for months? He'd asked Carl for help? He'd made Norm—well, okay, Perry thinks, the evil scientist would probably take any opportunity to kick the robot man out of his closet, but still… Heinz Doofenshmirtz, the man who had never had a birthday party, had planned one for his nemesis, and had managed to keep it secret this whole time.

Perry suddenly can't see very well. He blinks a few more times, and his vision returns. He's glad he's a platypus, because if he were human his voice might come out a choked squeak. Instead he makes his usual chatter. Heinz looks satisfied. "I thought you'd say that!" he says happily. "Norm, cut the cake!"

The giant robot's arm folds into his body, and then folds back out as a massive cake cutter. "Triangles or squares?" he inquires brightly.

"It's a cake, Norm, not a sandwich, it's a circular—just cut it the way you cut a pizza! A circular pizza!"

"Aye-aye, sir!" Norm responds. He still cuts it into squares.

A few minutes later, they're sitting on the couch, munching on pieces of rich chocolate-and-cherry cake and watching The Loud and the Lovely. "Yunno, Pe'wy the Pwat-apus," the evil scientist says around a mouthful, and then swallows. "It wasn't easy stirring all that cake batter. I had to add individual bowls of batter to the giant bowl before I used the giant mixer. It's a good thing I have a very durable mixing spoon, huh?" He smiles at the platypus sitting next to him. Perry pauses with a forkful of cake halfway to his mouth. "I'm talking about your nemeversary present," Heinz explains unnecessarily. Perry is suddenly having vision problems again.

He stares straight ahead at the television, the cake still not having made its way to his mouth, and makes the faintest of sniffling noises. He will not cry in front of Heinz. The time on Dr. Feelbetter had been enough.

His nemesis notices Perry's expression anyway. "Aw, don't worry, I'm sure Monique will come around," he says comfortingly. The agent is glad to have an excuse to be emotional, so he nods. "You realize we're going to go back to being arch-enemies tomorrow, right?" The platypus nods. "And that I'm going to come up with a stupid plan and trap you and you'll thwart me, right?" Perry nods again. "Nothing's changed, has it, Perry the Platypus?" Heinz asks, and his friend shakes his head. "Nothing's ever going to change with us." Perry nods. He scoots closer to his companion on the couch and lays a small teal paw on top of the man's.

"Good," Heinz says, turning his hand over to clasp Perry's. "I like us the way we are."

Perry couldn't agree more.

—THE END—

A/N:
Thanks again for reading. You're amazing. Yes, you. And you should totally drop me a review, even if it's a short one. ;)