Okay, so if cereal box mash-ups generally don't work, why do Kool Aid Man mash-ups work? He's been the Incredible Hulk. He's been Randy "Macho Man" Savage. And here he is with his manic energy fueled by caffeine in its most pleasant form. And they all work!
Maybe it's because unlike a lot of mascots, Kool Aid actually has some personality beyond "loves cereal" — even if that personality is just general enthusiasm, a gravely voice, and a blithe disregard for the structural integrity of buildings. Plus, his design is so simple and iconic that you can tweak it in a million different ways and still have it be recognizable.
I guess what I'm trying to say is, I like this shirt. And also maybe that no, I am not eating coffee grounds right out of the bag.
Though I'd also be lying if I said I'd never done that.