(Disclaimer: I don't own Invader Zim.)
In typical angsty-fanfic-Dib fashion, Dib walked into his bedroom and sighed for any and all the reasons Dib sighs in fanfics. You know the drill; do I really have to bore us all to death and go over it again? Family, Zim, school, Zim, (lack of) friends, Zim, puberty, Zim, the stupidity of humanity, Zim, Zim, Zim. All were factors in this kid's depression, especially Zim.
He wasn't counting on said central factor to be standing on his bed waiting for him, entirely out of disguise and smiling smugly. But there Zim was, alien eyes gleaming red as blood. Dib was more than a little caught off guard.
"Z-ZIM? What are you - "
"Pitiful Dib-human!" Zim chuckled. "Seven years!"
"Huh?" Okay, he'd lost Dib there.
"I've been on this planet seven years, earth-monkey," Zim clarified. "By Irken standards, you're still a smeet. But in seven years, I've watched you grow as big as your oversized head."
"My head's not - !"
"Foooolish HUMAN!" Zim strode to the edge of the bed and grinned up at Dib nastily. "How can you hope to defend your pathetic planet, when by the time I need to trim my antannae again you'll be old and DEAD! DEAD, I SAY!" Dib was silent (not that it mattered when Zim was talking). He'd never thought about it before... just how long did Irkens live? When his children's children had children, would Zim still be spouting off maniacally about humanity's defeat? Or, if Dib didn't live long enough to stop Zim... would the alien, perhaps, succeed?
"Then I'll just have to stop you before then, ZIM," Dib said, cockiness returning. "Besides, I know enough about your species to know that they consider tallness a good thing. Just go ask your 'Tallest.'" Zim, still the size of a small child, growled.
"TALL doesn't mean OLD, earth-stink!" Zim snapped. "Don't you get it! You may be tall, but your life is pathetically SHORT!"
"What's your point?" Dib frowned. "And why are you in my room, anyway?"
"I JUST MADE THE POINT! GRR! IDIOT!" Zim gritted his teeth and pulled on his antannae, then released and raised up on metal legs that came out of his Pak, towering over Dib. "How much older do you think I am than you? GUESS!"
"Uhh... twenty years?" This was getting a little unnerving.
"TWO HUNDRED! TWO HUNDREEEED!" Zim was getting worked up, but didn't he always? The alien paced the room anxiously, still walking on the metal legs. "In just ninety years you'll be DEAD, Dib... one hundred eight years old and DEAD! Maybe younger!" Dib jumped back as one of the legs got dangerously close and glared at Zim.
"What! Do you think I can change it?" Dib demanded, growing angry. Why was Zim so upset?
"FOOL! Of course you can change it! If you can stop Zim a thousand times, why can't you stop your own aging process!" He glared back at the human accusingly. Dib didn't know what to say to that. Zim pulled away and turned away, hopping back down on the bed as the metal limbs retracted. "Stop getting old, Dib-monkey. Don't die before I can kill you." He approached the window, and Dib realized he was getting ready to make a dramatic exit. For some reason, Dib didn't want that. So he stopped him in the most effective way he knew how; he leapt up on the bed and grabbed him.
"AARRRGH! LEGGO! STUPID EARTHENOID!" Zim's tiny legs kicked Dib hard, leaving prominent marks under the shirt.
"I'm not going to let go," Dib said coolly, clutching the struggling alien tightly with both arms. "Not until you answer my question: why did you break into my room?"
"You break into my base all the time," Zim reminded him.
"Okay..." Dib conceded. "But that's not an answer! Did you just break in to yell at me for getting... OLD? Or do you have some kind of evil alien scheme all plotted out?" Zim had stopped kicking, and was unusually quiet. "Well?"
"Don't yell at me, stink-beast," Zim muttered. Dib looked down at the green creature in his lap perplexedly.
"I wasn't yelling! ...Maybe a little, but only because you did!" Zim said nothing. Dib shifted his grip on the alien a little, feeling awkward; what was this about?
"I don't want you to die, Dib," Zim said finally. Dib inhaled as if to say something ("Then why are you are always trying to kill me?"), but was too dumbstruck to do so. Finally, he exhaled and nodded.
"...I know," Dib responded. There was another silence. Dib was keenly aware of the alien - of ZIM's body nestled in his lap, held in his arms. He noticed Zim's arms clutching his. And before he could complain, he realized he liked it. It was comforting. There was no reason to move; Gaz and Professor Membrance never had any reason to enter his room, and Zim didn't look like he was going anywhere. Cautiously, Dib relaxed, holding Zim in a less constrictive, more affectionate manner. Zim didn't protest. After a while, he even turned around and hugged him back.
For a long while, they just stayed like that.