After several years of working full-time around Information-Age high school students, this summer I've finally picked up an addictive Homestar Runner habit. And I must confess that it's brilliant. Homestar Runner surpasses other Flash cartoons like Strindberg and Helium (when will they add a new episode?): while the Internet is merely a distribution mechanism for other cartoons, H*R fully embraces the possibilities of the Internet medium. Thus, there are numerous opportunities to interact with the cartoons by clicking on things. When a cartoon includes a song, there is often a link to download the mp3 immediately. One of the characters has his own website, and another has a LiveJournal-esque blog. (The Simpsons has used similar gimmicks recently, with WhatBadgersEat.com , sexyslumberparty.com , and springfieldisforgayloversofmarriage.com .) You can email the characters, and one of the most popular features involves Strong Bad checking his email.
The email that most exemplifies this surreal embrace of the Internet (among those that I've seen so far) is "virus". Continuing in the tradition of "Duck Amuck", the characters are forced to interact with the medium that created them. When Strong Bad's computer gets a virus, the entire Homestar universe is thrown into pandemonium as pop-up windows start popping up and characters' faces turn into broken JPEGs. The characters valiantly rage against the dying of the light, in a sequence reminiscent of the climactic sequence of Eternal Sunshine of the Spotless Mind.
(Warning: if you haven't watched a few H*R cartoons already, this one probably won't make any sense. This wiki is a good place to start.)