This wasn't possible. It just wasn't possible. The boy completed yet another frantic lap of his room, before giving up on pacing and collapsing heavily onto his bed. The black coat slipped off the headboard and flopped down over his face.
"Uugh…" Dib weakly batted the thing away, turning his head to face the wall. He couldn't even bring himself to look at it now.  The wall was safe; all his Zim photos (for science, of course) had long ago been pulled down and stashed carefully away in his father's lab, in one of those cupboards that no one ever seemed to use.

Barely an hour ago, he'd burst screaming into the Membrane household, somehow managing not to stop once after fleeing the library. Luckily the place was free of his beloved kin, who were still away on their little trip.
He'd forced down a glass of water in an attempt to calm his nerves (his heart was still going like a jackhammer), and then staggered weakly up to the bathroom to shower. It wasn't until he took off his coat in the bathroom to hang it up that he noticed, for the first time, the liquid that had splattered onto him when he attacked the creature in the dark. He sniffed at it, finding it to have a subtle, almost metallic smell, and then wiped a finger over the wet patch so he could see the substance more clearly. That was when Dib had practically jumped out his skin, mind reeling in shock, slipped on the bath mat and had to grab the towel rail to save himself. Lurching to his feet again, he'd stumbled over to the sink to stare desperately into the mirror. As he thought, there were spots of the liquid on his face as well, standing out stark against the backdrop of his now exceptionally pale skin. A scene from three years ago was ripping through his memory. Dib knew exactly what it was he was looking at – nevertheless, he'd wasted no time in sprinting downstairs to his father's lab to find a swab.
Finding the least contaminated spot he could, the paranormal investigator had carefully swabbed a tiny amount of the substance onto the cotton, sealing the precious sample in a sterile bag (his father always had these things handy) and racing back upstairs to find the next thing he needed.
Dib laid down the half-full test tube next to the bag which contained his sample, staring hard at the contents of the two. They definitely looked similar. But perhaps there was a chance he was wrong? Unlikely, but possible. Human eyes couldn't distinguish DNA, after all, could they? He needed a pair of alien eyes to look at this… no, don't think about that… human technology would do.
Still fearing the worst, Dib had gone about the procedures for DNA extraction, luckily he knew his father's equipment like the back of his hand. SDS. Centrifuge. Ethanol. Centrifuge. Wait. Now extract the DNA, and dye it…start electrophoresis…

Dib lay prone on his bed, trying to calm the thought that were still racing around his mind like a headless chicken. Most of them were confusing, and tangled, and not very helpful. Part of him was murderously impatient to see what the results would be, but another part huddled in the dark corner of his mind, whispering discouraging thoughts. He took out his headphones, hoping to drown out the thoughts with some music. Ten minutes later, he was just starting to calm down when the deafening blare of his alarm snapped him back into reality. The electrophoresis was done, and he should now be able to compare the samples.

A match.

Dib's hand trembled as he picked up the tiny vial lying on the table, the sample he had collected over three years ago. There, the truth was out. You couldn't argue with science, even though he now realised he'd been able to see the similarity instantly. He sat heavily on the bed, hand over his chest as his heart was pounding almost as hard as when he'd done that mad escape only a few hours ago. The scene from earlier repeating over and over in his mind like a scratchy record, he stared down at the coat on the floor, stained with what Dib was now certain was Irken blood.

And there was only one Irken it could possibly belong to.