A twag is a tag in the Twittersphere.
In 2009, after interviewing Randall Munroe about his xkcd Web-comic, @resila was inspired to launch Twaggies, a crowdsourced comic. But because @resila couldn't even draw a stick figure successfully, much less a twaggie, he cajoled @yaelbt, and others into handling the goods. These days, Twaggies are doodled by more than two dozen amazing illustrators and artists, including @barneda, @KevvoCoffee and many others.
Twaggies creates original comics for Mashable.com, as well and is syndicated daily over on GoComics.com.