This has precedent too because he actually does put on a disguise that bad in the Xmas special and Zim is completely fooled by it.
Funniest way for Dib to disguise himself as an Irken would be to do it literally the exact same way as Zim. Just split his cowlick in two to make it look like antenna and put in some Irken-style contacts and he's done. He doesn't adopt Irken-style clothing or try to hide any of his alien features except his eyes. Anybody asks why he's not green and has ears sticking out of his head, he just says "It's a skin condition". Even he can't believe it works, and Zim is seething because now he knows how Dib felt all those years. Like, "Really? No one sees through that? SMH I'm so embarrassed by my species right now."
Thinking about Dib growing up surrounded by guys who can't wait to lose their virginity at the first opportunity and being told he's a loser because girls aren't interested in him. But when he finally has an opportunity to have sex with someone, he turns them down because he doesn't want to lose his virginity just for the sake of losing it. He wants his first time to be with someone special, even if another chance won't come along for a long, long time, if it ever does. But then one day, Zim makes a move on him, and acting purely on instinct, not thinking about it at all, he goes all the way with him. It's only afterwards, when the post-nut clarity hits, that he contemplates whether he just wasted his first time on an impulsive fuck with someone he doesn't even like, or if Zim was really that "special someone" he was holding out for all along.
Tired: Tak couldn’t hypnotize Zim because that device just doesn’t work on Irkens. And she can’t hypnotize Dib and Gaz because they’re just too Smart.
Wired: Tak’s device depends on the target looking her in the eyes to work and every IZ main character is far too Autistic to actually make eye-contact.