Disclaimer – I don't own Voltron. There are quite a few theories floating around regarding Keith having alien DNA, but one of the theories doesn't really pan out.

Aliens Among Us

"What if aliens visited Earth?"

"Aliens already visited Earth, Hunk." Pidge didn't look up from her computer.

"That's not what I mean." Hunk's mouth twisted into deep concentration, one hand placed on his chin as he did so.

"I'd rather not think of the Galra attacking Earth. My mama's still there." Lance lay on the couch in the resting room upside down, his legs going over the back, boredom getting the better of him. A rather dejected look appeared in his eyes, making his usual smirk disappear.

"No. I mean..." Hunk's mouth twisted into a pout, his eyes widening like they did whenever something worried him. His voice lowered to a rather loud whisper. "What if aliens visited before, and you know, intermingled with humans? You know, like intermingled?"

Keith stared at Hunk, his facial features blank with confusion, but Lance waved a hand, his mouth uttering the first thing that came to mind. "Purple."

"What?" The red paladin's confusion continued.

"Any kid of a Galra and a human would be purple."

The shortest of the males stared at the other paladin's, rather dumbfounded as to how the conversation came to be about alien hybrid babies, only for the corner of his mouth to twitch at the weird conversation. The sound of computer keys clicking stopped. "Lance, we would have known that, or the child would have been kidnapped by the government and experimented on. You do realize that, right?"

The red paladin let out an irritated sound. "Actually, with what they hid from us regarding the Kerberos mission, I doubt we'd ever know, as they'd keep purple kids under lock and key."

The teen leaned over, wondering what project Pidge was working on, only to receive a glare. Neither one expected Lance's next comment. "Maybe the kid camouflages itself?"

Pidge glared at Lance this time. "That's an Altean trait, not a Galra trait."

"Well, maybe they're like, you know, the same species?" Lance pulled his arms behind his upside down head, his lips pushing together as he attempted to think. Keith and Pidge's faces drained of emotion, their faces blank due to the confusion resulting from Lance's new statement.

"Oh!" Hunk's mouth twisted into a smirk. "Like Romulans and Vulcans, right?"

Pidge pushed up her glasses while Keith continued to give everyone a blank look. "Well, maybe."

"Romu... what?" Keith's eyes blinked a couple of times, his mind not comprehending what Lance said again.

"You know, Star Trek?" Lance raised an eyebrow only for the red paladin to continue giving him a blank look, the tension between the two growing. "It's a sci-fi series."

"Oh, like Gundam?" Keith's facial features softened as some kind of recognition occurred.

"Like what?" It was the blue paladin's turn to be dumbfounded.

"Big robots..."

Lance stared at the shortest of the males. "No, I don't know any series like that. Except..." A laugh escaped his mouth. "... the kid's shows my little brother likes to watch."

"Gundam's not a little kid's show."

Keith opened his mouth to protest, but Pidge spoke first. "Well, I always wondered why there weren't more differences between the Romulans and Vulcans, let alone more species variance." A silence fell over the room. "You know, there are multiple human races, so why aren't their human races on earth? So maybe Altean is like one race, and there are other races out there."

"So there is merit to my theory!" Lance let out a laugh.

"Altean's aren't purple." Keith's body became slack, as the conversation

started to annoy him.

"Maybe purple's dominate genetics wise, but light skin is not." Lance piped up, rolling over so that he could start into a sitting position, his excitement growing.

Keith pushed himself up from his own slack position, a flash of anger in his eyes. "Wait..."

"Not finished. It's how genetics work for skin, right. Meaning a human hybrid could have purple skin 'cause it's the dominate color, right?"

"I'm quite sure that's not how genetics work."

Lance pointed a finger accusingly at Keith. "So, you actually know how genetics work?"

"..."

"You don't know!"

"I may not know the jargon Lance, but I do know that's not how it works!"

"You're just..."

"Keith's right." Pidge let out a sigh, letting her body slide down, her hands holding onto her now closed computer.

"What?" A blank face appeared on Lance's face, the excitement gone.

Hunk rubbed the back of his head. "You're confusing the amount of pigmentation has with the actual color."

"No, I'm not. You and I are darker than Pidge and Keith, thus different color."

"No. You're darker in color because you have more pigmentation." Pidge's mouth twisted into a frown.

"Same thing."

"No, it isn't. Darker in color is still the same color. We're talking about an actual change in color."

Lance slunk down, the look the green paladin gave him proving to deter his good mood greatly. "Let me guess. You've got more ways to blow a few more holes into my theory?"

"Yeah, if we're going with the idea that the purple skin is a dominant trait, then the ability to camouflage - if the two were the same species - would be a recessive gene. That's based completely based on the idea that they're the same species, because if they're not, the Galra can't camouflage themselves, and it wouldn't be passed on to their children at all." Pidge watched the baffle look. "Purple skin can be considered to not be a rare trait, but camouflage is."

"Wait..."

"They mean a human-hybrid of the Galra would not be purple." The red paladin glared at Lance.

"Shut up Keith!"

"No, I didn't say that. I said that they wouldn't be purple and have the ability to camouflage," Pidge said as the door slid open."

"What are you guys talking about?" Shiro stepped into the room, folding his arms across his chest.

"Talking about?" Hunk sat up straighter. "We're discussing if a Galra-human hybrid would be purple, but also inherit the ability to camouflage themselves."

Shiro stared at the younger paladins before crossing his arms, his mouth twisting in a rather bemused manner. "Nope. Camouflaging is an Altean trait, not Galra."

"Yeah, but what if they're like the Romulans and Volcans?"

The black paladin stared at Lance.

"What? You don't know Star Trek like Keith?"

"I actually know about the series." Shiro let out a sound of exasperation. "I'm not exactly sold on them being the same species, but I also don't recollect any of the Galra having this ability either. Even if the Galra did have this ability, the chances of them passing on both purple skin and the camouflage ability to their kids are slim. If the kid did get the camouflage ability, it would likely be faulty due to mixing with the human genetic structure, or even because they aren't trained to use the ability."

Keith leaned against the couch again, a rather bored look on his face. "What if the purple coloring isn't genetic either? What if it's something which resulted from them doing something they shouldn't, that broke from Altean culture. That would explain the purple skin, but also explain why they can't camouflage."

"Gross. What would turn the skin purple?"

"I don't know. That weird purple stuff maybe?"

"Nuh-h. I think it's still possible..."

"Sorry Lance," Shiro shrugged his shoulders. "If Keith is right, no purple skin. It doesn't make it possible."

"I'm saying his isn't possible."

"Yeah, but a hybrid managing to inherit such a nifty trait?" Hunk shook his head. "I believe in the purple skin more than I do the camouflage ability if we're talking possibilities."

"So, you're saying no human-alien hybrid?"

"We didn't say there can't be a human hybrid. The camouflage is definitely an Altean trait, and the purple skin is a Galra trait, so them showing up in the same individual hybrid just wouldn't happen." Pidge looked at Lance as if he were crazy.

"But that's a really big secret to keep, purple skin! They would need the camouflage ability?"

Pidge sighed, shaking her head. "What don't you get about Alteans and Galra being the same race?"

"But we did discuss the idea that they were the same race!"

The green paladin narrowed her eyes. "If the color of purple is a dominant trait, then camouflage would be a recessive ability, so they would have no way to hide it."

"That would mean if we knew someone who was part Galra, they would not have purple skin." Hunk brushed a hand across his forehead. "That's good to know."

"Wait..." Shirt shook his head, moving to sit down on the couch next to Pidge. "Exactly how did this conversation start? You guys aren't trying to accuse each other of being a Galra spy? Because that is ridiculous."

Lance opened his mouth, only for the yellow paladin to speak sheepishly while twiddling his thumbs. "Well, I kind of asked if there were alien hybrids on Earth, what they would be like."

"That was rather a random Hunk." Shiro's eyes twinkled with mirth.

"Specifically, though I was wondering if maybe survivors of Altea somehow found their way to earth, blended in, and had babies with humans. Not Galra though. That was all Lance."

"I guess not as random as I thought."

Lance's mouth twisted up, not noticing the weirded out look Shiro now had on his face. "What if one of us were part Altean or even part Galra?"

Keith frowned. "If one of us were part alien, and knew it, don't you think that's something they'd have told everybody back when Pidge told everyone she's a girl?"

"Uh... well, what if we didn't know?"

Keith's mouth opened and closed at Hunk's statement as the yellow paladin's face paled quite a bit. Shiro rubbed the back of his neck. "Well, I think that rules out the person having purple skin. I mean, how could you not know if your own skin is purple?"

"Yeah, a person would certainly know if they were alien then, and have told everybody else. Even I got that." Keith stood up. "I'm going to go and train."

The red paladin left the room. Lance pointed his thumb at Keith, deciding to crack a joke at the other's expense. "Anybody else wonders if Keith's an alien."

"Not funny." Shiro shook his head, before getting up to leave himself.

"Keith would have told us if he were part alien and knew it." Pidge went back to her computer.

"That's mean Lance. You just accused Keith of keeping a pretty big secret from us." Hunk shook his head. "Plus, there are other reasons for him to act the way he does."

"Like?"

"Well, by your logic Lance, you're at least part alien because you don't act normal." Pidge piped up.

"No. I'm the only normal one here."

Note - One of the theories I've come across is that Keith, as a Galra-human hybrid would have purple skin, but also have the ability to camouflage the fact he has purple skin. However, the camouflage ability is an Altean ability, not Galra. Keeping this secret wouldn't have been easy, particularly back on Earth, but when Pidge revealed herself to actually be a girl, that would have been a good point for Keith to reveal he was Galra-human and had purple skin, as they as a team was supposed, to be honest with each other. It makes more sense if Keith is part Altean or Galra that he doesn't know. Thus no purple skin, or other oddities.