xkcd: My dad said flu vaccines are linked to autism, so to be safe from swine flu I'm trying to lick an autistic kid.

Lots of comics have been making jokes about Twitter lately, and they've mostly been lame. What sets this xkcd apart is that it's not so much about Twitter as it is about swine flu. Which is to say, most of the comics have been using Twitter as a joke in and of itself, whereas this cartoon is using Twitter as a vehicle for a joke about something else. It works much better.