User blog comment:YoungOtakuNerd/Crossover Shipping?/@comment-24111359-20140609143119/@comment-4797970-20140609195847

Yup. The reason I came up with Marcewin was 'cuz of similarities.

While the obvious reason is that they're both vampires, there's more reasons why it makes sense. For instance, it's implied that Marceline's relationship with Ash (her ex-boyfriend) was dysfunctional; she even said herself that he was a psyco. Compare it to how Irwin's crush on Mandy never works out, and all she does is abuse him whenever he's around her, no matter how nice he is.

Then there's the contrast in personalities. Marceline is cool and mischievious, and would probably be kinda like your cooler big sister (metaphorically, of course). Irwin, on the other hand, is dorky and sweet; he's usually nice and tries to stay out of trouble. The way their personalities differ is cute and funny, and it makes the pairing cool.

I mean, just imagine if CN were still in its CN City era; they could've done a bumper where Irwin and Marceline go on a blind date, only for hilarity to ensue!