It sometimes seems like there is a general "Internet aesthetic", a general shared taste among Internet users (with exceptions, of course) that sometimes transcends subgroups. But it's a taste for things that society outside of the Internet would tend to think of as pointless, ridiculous, insane, stupid, or wastes of time. The "Zero Wing" phenomenon could only have been generated by the Internet, not just because of the ease of dissemination, but because the Internet audience seems geared towards an appreciation of the absurd and frenetic (the original opening isn't particularly hyperactive, but the Flash video certainly was). Similarly, the Monkey Pit (an example of which is still, I believe, hiding on itswalky.com) is the sort of head-scratcher that could only be nurtured on the 'Net. Gene Ray is just another nutcase in the "real" world, the sort you'd find standing on a streetcorner wearing an incoherently lettered sandwich board and ranting at all and sundry, and who you'd cross the street to avoid, but on the Internet he's considered a sort of mad genius of comedy (a status he would doubtless not appreciate). Pokey the Penguin. Homestar Runner. Yatta. The epilepsy-inducing pop culture barrage of countless animutations.
This ludicroëclectic aesthetic (dare I call it a movement?) seems to combine aspects of dadaism, postmodernism, and punk: a mish-mash of cultural (usually pop-cultural) icons and tropes in service of no coherent central meaning other than being, frequently married to a punkish DIY approach. Influence from the "sampling culture" of hip-hop seems probable. The assertion of an "end of irony" made soon after 9/11, while frequently rejected since then, may have in a sense been correct: if everything is ironic (who knew Alanis Morissette was so insightful? Aside from Kevin Smith, who typecast her as the playful, omniscient God in his films), then irony ceases to be a useful concept in itself.
And with the Spongmonkeys advertising Quizno's on TV, if only for a brief moment, and Happa-tai appearing on Jimmy Kimmel Live, it seems like it's making incursions on the mainstream.