Fortunately, some things had changed in all those years; puberty had been at least kind enough to Dib so he could now dangle his superior height - literally and metaphorically - over Zim’s head. “Sorry, what’d you say?” he taunted, holding his prize high out of his enemy’s reach after snatching it from his claws. “I couldn’t hear because of how much taller I am!”

His moment of glory was cut short, however, as Zim launched himself at him with a hiss like a feral cat, sending them both crashing to the floor in a tangle of limbs and antennae. They were still surprisingly evenly matched; Zim was a lot stronger than his size would suggest, but Dib now had the advantage of longer arms and legs to attempt to hold him off as they wrestled for the device. He might even have been winning - right up until Zim grabbed his side, claws digging into the sensitive spot just below his ribs.

Dib yelped, reflexively slamming his arm down to protect himself; before either could do anything, the remote flew out of his hand and across the room until it disappeared under one of Zim’s experiment tanks. Instead of running after it, Zim took advantage of the distraction to seize Dib’s wrist, pinning him to the floor.

“Ha!” Zim loomed over him, now straddling Dib’s waist so his maniacal grin filled his whole vision. “You flesh-bags really are pitiful, cowering in pain from the slightest touch!”

“That’s not what that - was…” Dib froze, heat rising to his cheeks as his nemesis bore down on him, now painfully aware of his compromising position. Zim couldn’t - did he even know what tickling was? Because this would be a really bad time for him to find out.

“...Eh?” Zim narrowed his eyes, curiosity flickering across his face alongside the usual suspicion and irritation. “What are you smiling about? Why is your grotesquely ginormous head so red?!”

“My head’s not bihihig!” Dib bit down on his lip, but he couldn’t stop a few embarrassing giggles from slipping out when Zim jabbed at his ribs again. He struggled to bat his hand away, but with only one arm free and Zim basically sitting on top of him, he wasn’t having much success. “Quihihit ihit!”

A shiver ran down his spine as he could practically see his doom unfold along with Zim’s smile, sadistic delight sparkling in his eyes, and oh god no Dib thought he was prepared for anything but please not this, anything but this, he’ll never live it down…

“Well, well - you really thought you could conceal such a glaring weakness from me?” he demanded, mercilessly prodding and pinching his way up Dib’s side. “I’d...sort of imagined more writhing in excruciating agony, but this is rather amusing too, watching you squirm like the wretched worm you are!”

“Thihis isn’t fahahahair!” Dib spluttered between peals of laughter; he hadn’t been tickled since he was a little kid, but this was so much worse because it was Zim and he hated giving him the satisfaction but was equally powerless to stop his body from reacting as those probing claws dug right into his horribly exposed armpit. “Zihihihim!”

“Yes, yes, I am Zim!” his foe cackled, releasing Dib’s wrist to attack with both hands, one even scuttling under his shirt - which was so far beyond fair - and scratching at the tender skin almost hard enough to hurt, but his gloves dulled the sensation so it just tickled even more. “If I had known you were this easily incapacitated, I could’ve built a device to take care of you long ago! Now, laugh, pathetic Dib-thing - admit your annihilation, or perish in helpless hysteria at the merciless claws of Zim!”

“Nehehehever - !” Dib had not foiled so many of Zim’s plans to let him win this one by tickling him, of all the cruel and unusual methods. There was only one way to fight back, and he had no idea if it’d even work on an alien, but what else did he have to lose, more of his dignity? Arms flailing as he tried desperately to suck in his stomach before those treacherous claws could get to his bellybutton, he eventually managed to grab a handful of Zim’s side and squeeze it repeatedly.

Zim let out a squawk like a bird having its feathers pulled out, letting go of Dib as he scrabbled to slap his hands away. “D-do not touch Zim with your fihilthy meat-sticks!”

Huh - that sounded like a game-changer, and now it was Dib’s turn to grin like a mad scientist as he kneaded Zim’s sides like his life depended on it - which it might - until he had an armful of squirming Irken trapped in an almost-hug, one arm around Zim’s waist with his PAK pressing against Dib’s chest.

“What’s the matter, does it tickle?” he asked, smirking from ear to ear as he savoured the sweetness of revenge - and possibly the most important discovery of his career as a paranormal investigator. “Is the mighty Invader Zim ticklish?”

“Lies! Cease! Ihihi’m gonna destrohohoy yooooou…!”

It wasn’t like he’d never heard Zim laugh before - only like every day since they were at skool - but this was different; less controlled and mocking, more free and almost joyful, even if it was a joy forced upon him as he writhed, kicked and cackled under Dib’s skittering fingers, exploring the surprisingly soft and smooth skin under his shirt. It wasn’t exactly an autopsy, but the thought that he might be the first to hear - the first to make Zim almost squeal when he wiggled his fingers under his arms - that was more deeply, weirdly, sadistically satisfying than anything he’d imagined. “Wow, I think you’re worse than I am! So are all Irkens this ticklish, or is it just you?”

“Zihim is telling you nohothihihihing!” Zim’s laughter seemed to jump an octave when Dib felt around his back; the skin around his PAK was slightly raised where it was embedded, which was interesting, mainly for the way he bucked and squirmed frantically as Dib traced it with his fingers. “GIR! Where are you?! Do something to make this stohohop!”

“Yes, master!”

Dib looked up just in time to see Zim’s robot assistant propelling towards him at alarming speed, his eyes blazing red. Before he could move to shield himself, however, GIR came to an abrupt stop, eyes flickering back to cyan and his metallic mouth stretching into its familiar hyperactive smile. “Ooooh! Tickle fight! I wanna plaaaay!”

“Now, GIR! Fire the - wait, no, what are you doing?! Put that back!” Both Zim’s and Dib’s eyes widened - in horror and intrigue respectively - as GIR plonked himself down on one of Zim’s legs, picked up the other and pulled his boot off. Dib had never actually seen his feet before, he realised; he had three toes, clawed like his fingers but a little shorter. Judging by how he scrunched them up when GIR prodded them, they were also pretty sensitive.

“This li’l piggy went to Foodcourtia,” GIR chirped, wiggling a toe; Zim made a strangled noise of protest and attempted to pull away, but Dib was still holding onto him. “This li’l piggy went home - aw, we outta piggies! And thiiis li’l piggy…”

“GIR - nooo!” Zim begged, and Dib could actually feel him tremble in his arms as his toes curled in anticipation of what was to come. “Don’t do this! You’re supposed to attack the intruder, not -“

“...went weeweeweeweeeeeeeee…!” GIR hugged Zim’s foot and scribbled furiously all over it, his tiny metal hands a blur as his master shrieked with laughter, helpless to escape his ticklish doom.

“How’s it feel, Zim, betrayed by your own minion?” Dib snickered along with him as it occurred to him he should probably be recording or taking photos of possibly the greatest moment of his life to date, but holding Zim captive and laughing helplessly was way too satisfying, tickling under his arms while GIR happily went to town on his foot. “Maybe I’ll just keep you like this - you’re not much of a threat to the Earth when you’re just a cute little giggly alien puddle…”

“Wh-whahahahahaaaaa?!”

The sheer incredulous outrage in Zim’s voice tore through the air, and Dib couldn’t help but wince, recoiling as the ear-splitting screech assaulted his eardrums. As his grip loosened, Zim wriggled free and kicked GIR off of him, scrambling back to his feet, and the chaos was replaced by an unusual and equally uncomfortable silence. (Apart from GIR eating popcorn out of his head as he watched them, and that was the most normal thing about this situation.)

“I - uh...“

“He thinks you cuuuute!” GIR giggled, grabbing Zim’s cheeks and squishing them together comically.

“No I don’t!” Dib felt his face flush under the spotlight of both GIR’s carefree smile and Zim’s laser-beam glare, the protest coming out just a little too quickly. “I was teasing you - it’s just a thing people say when they…”

He trailed off, because man, things had gotten weird, even by their standards. But this was still Zim, and he was still a jerk and evil and the total opposite of cute, even a little breathless with his clothes all rumpled and one foot still bare, antennae lowered and quivering and what looked suspiciously like an olive-coloured blush staining his cheeks. That warm feeling was just Dib enjoying the sight of his enemy humiliated in defeat, like anyone would. Right? That made sense.

“Give me my boot, GIR.”

“Go long!”

Zim caught the offending item without looking, but instead of putting it back on he hurled it at Dib, who dodged just before it smacked him in the face, bouncing off his shoulder instead.

“Ow - hey, that’s sharp!”

“Good! Suffer! That’s what you get for trying to taint the mighty name of Zim with your disgusting lies like…” He screwed up his face as if he could barely bring himself to spit out the word, making dramatic finger-quotes, “cute!”

“Okay, geez! It’s not like I meant it…” Dib rubbed his shoulder, shifting awkwardly - he wished they’d stop repeating the word like that. But even this momentary weirdness couldn’t change the fact that he’d just uncovered a significant weakness in his nemesis, even if he inconveniently shared it. He’d be an idiot not to exploit this for all it was worth, a smug grin tugging at his lips again as he picked up Zim’s boot. “But thanks for this. I bet I can get all kinds of useful evidence from a genuine article of alien clothing…”

“You…!” Zim’s eyes almost bugged out of his head as he let out an indignant splutter - only to break into a dangerously familiar smile before activating his PAK legs, towering over Dib with a renewed gleam of vengeance in his eye. “Enjoy your last few seconds of freedom, Dib-worm - we shall soon settle who is cute!”

“I’d like to see you - wait, what?!”

Dib didn’t have time to figure out what Zim meant by that as he darted for an escape route, still clutching Zim’s boot - but when he was quickly seized and hoisted into the air by a pair of metal spider legs, he was pretty sure things were only about to get a whole lot weirder.