Disclaimer: You know I don't own any of this…

-x-

Zim awoke to GIR shaking him violently, "wakey-wakey master!!!!!"

He sat up blearily and rubbed the crust from his eyes, "What time is it?" he groaned, human bodies were so needy: twelve hours of sleep, constant food and fluids, relieving oneself of the excess waste, the list went on and on.

"six! just as you told me to!!!!!" GIR was shaking, "and all I had to do was play with piggy and minimoose for fourteen hours straight and your masters called to see how you were doing and-AAAAUGH!!!!!!" he screamed and then ran face-first into the wall.

[NOT VERY SMART, IS HE?] The computer drawled.

"You're one to talk…" Zim grumbled as he got his stuff together to go to Skool, and then he stopped abruptly. Something was off…but what? He opened his mouth again and shouted, "GIR, get up!!!!!" There it was. The pitch and timbre of his voice changed in that instant, going from his normal pitch to a high squeaky one and it seemed to pause in-between those two stages. "Computer, voice analysis!"

[YOUR VOICE JUST 'CRACKED']

"Define."

[A SYMPTOM OF PUBERTY. WHEN A VOICE 'CRACKS', IT CHANGES PITCH DRASTICALLY CREATING A CRACKING SOUND IN THEIR TIMBRE]

"Puberty? Define"

[PUBERTY: THE STAGE IN-BETWEEN THE SMEET AND ADULT STAGES OF HUMAN LIFE WHERE A HORMONAL IMBALANCE CREATES A DRASTIC CHANGE IN THEIR PHYSICAL FORM, AND THEIR MENTAL PROCESSES. VARIES FROM MALE TO FEMALE]

"WHAT?!!!!!" His voice cracked again, "Computer, analyze hormonal levels and compare."

[ANALYZING...HORMONAL LEVELS DANGEROUSLY HIGH. CONCLUSION….YOU'RE GOING THROUGH PUBERTY]

"High?!!!! This can't be…." He bit his nails (a habit he found revolting), "Computer state symptoms of male puberty."

[PUBERTY IN A MALE HUMAN IS USUALLY CHARECTERIZED BY A SUDDEN GROWTH-SPURT, CHANGE IN VOICE PITCH, CHANGE IN MOOD, AND CHANGE IN MENTAL PROCESS]

"Dib" he spit the word out in pure hatred, "That worm again!!!" he turned to face the squealing GIR who was flopping on the floor like a kid having a seizure, "GIR! Go get our friend Dib and bring him here."

"aw…so you're friends now? that's cute…"

"NO! I am NOT friends with that traitor!" he was seething. "Go get him now"

YES MY MASTER!!!! GIR flew off.

-x-

Dib landed face-first on the floor, right by Zim's feet, "Um….h-hi Zim…Did you sleep in that?" he suddenly covered the place his nose had been and winced, "You stink…"

"Yeah well, it's no thanks to you, you pitiful excuse for an Irken. Thanks to your genetic meddling, my entire being is changing in ways that cannot be comprehended by your puny minds!" Zim pouted.

"What changes?"

"I said you couldn't comprehend it!!!" Zim's voice cracked again. Seeing the look on Dib's face, he blushed a deep red in embarrassment.

Dib got this sly look that resembled that of a snake, "You're going through puberty, aren't you?" Zim shook his head, "No, I know it, you are going through puberty. You are!" He looked smug, "I knew that the Irken cells would speed up the assimilation process, but I didn't know that they'd make you accelerate into the teenager stages so quickly! I mean, I used my cells so…" his face lit up, "SWEET!!! I'm gonna go through puberty before the age of thirteen!!!" He did a little happy dance, GIR joined in.

Zim was seething, "YOU!!!! FIX THIS - NOW!!!!!!!"

Dib stood amazed, "Fix what?"

"This 'puberty' thing. Fix it!"

"Well….I can't"

"Y-What do you mean you can't?!"

"It's a chemical change, even if I wanted to, I couldn't stop it. You have to go through it in its entirety." Dib was serious, "Besides, at the rate you're growing, if I change you back, you'll be as tall as the Tallest if not a few inches taller."

"Wait, what?!!! You said 'if I turn you back'!!! What do you mean 'if'?!!! And why would I remain the same height?!"

"Well, unless you cure me, you're stuck like that so that 'if' is dependant upon you and your actions. As for the height thing, when you turn back into an Irken your skeletal structure doesn't change all that much so you'll remain about the same height as you were in your human form. That will probably confound the Tallest…"

"YOU LIEEEEE!!!!!!" Zim's motto was, 'If you don't like it, accuse them of lying'. "There is no way on Irk I could be taller than the Tallest! That would be heretical!"

"Well…that's your issue then… and-" he paused and made a face, "Take a bath…please…" Dib ran out the door and hightailed it to Skool, disguise in place.

Zim stared at the running boy; "I really hate him…" his hate was half-hearted though. Something inside of him had changed; he seemed to hate the Earth and the humans less and less with each passing hour. It unnerved him to no extent.

-x-

Zim skipped Skool that day and went sightseeing as a human for the first time. He just walked around the park, the city square, the beach, and enjoyed the scenery. Somehow, he had this odd respect for the humans now. They could survive when bogged down by pollution that was only matched on Vorgas III, when faced with world-wide hunger, when faced with impending war, when faced with natural disasters, even when faced with an alien invasion they still seemed to build their nation back from the ashes and ruins to survive longer and adapt. They truly were an interesting species, even if their life-expectancy was low and they were a bit stupid and shortsighted.

Why do I even care?! He thought, Why do I even give a flying flip about these creatures?! Why did me changing into one of them make me so weak?...Then he sat on a bench and put his head in his hands. Irk this is confusing…

-x-

Dib was surprised that Zim didn't come to Skool, though he couldn't blame him, his appearance had changed so drastically that he probably couldn't brush it all off as puberty What surprised him more was that he was waiting for him at the stoop of the Skool looking a tad confused.

"Zim?" he asked concerned, "Where were you?"

"Nowhere…" Zim sighed and then he gave Dib a strange look, "I see why you like this planet so much…it's a very nice place."

"…are you okay?"

"yeah…not really" he sighed again. "I think I may have the brain worms…"

"Why?" Dib quirked an eyebrow in genuine concern.

"Well…I seem to be developing feelings for your people, I-I enjoy the heat of your star on my face, the feel of the breeze in my hair, the smells of the food that you cook and eat…I-I don't want to destroy this place any longer! I actually like it here---!" He began to cry.

Dib smiled softly, "Don't worry Zim - it's just a sensory overload. You're experiencing what we humans call empathy, or the ability to relate with other humans. It's only normal..." He patted his back gently.

"But I'm an Invader!!!!! I'm not supposed to relate to the natives on my planet, I'm supposed to hate them or at least feel apathy towards them!" He began to sob, "How am I supposed to face the Tallest now that I have identified with you humans?!"

"Well…"

Zim's eyes opened wide and he looked back at Dib in shock, "The Tallest!!! GIR said that they had called and that they were wondering where I had been!!!! What if they had seen me like this?! Me, the amazing Zim fallen to human form!!!! They would have good cause to exile me to some unknown obscure planet for the rest of my life cycle!!!" Dib just grinned knowingly. He then got up and looked down at his lanky form in disgust, back to his full egotistical, human-hating self. "Fine-!" he spat in Dib's direction, "I'll play your little mind game, but you'd better have that cure ready by the time I see you again or you'll regret the day you ever messed with Ziiim!" Then he ran off.

"Well that was unexpected…" Dib shook his head and laughed, "Well, I'd better go get that cure ready."

But neither of them had their hearts truly in it for some odd reason.

End Evolution

-x-

A/N: This ended quicker than I thought…ah well. On to the next (and final) segment. Hope you enjoy this! Sorry if it came off as ZADR-ish…that was unintentional.