Apparently the Penny Arcade guys are fairly close with Telltale. Telltale's had a big presence at PAX, is a sponsor for Child's Play, there have been ads for TOMI and other Telltale games on Penny Arcade's site (and they're pretty selective about what they advertise, I think) and they even included the first episode of On the Rain-Slick Precipice of Darkness in the Great Adventure Bundle. So Tycho's in the same reason Heavy's in: the people who own them just really like Telltale. (Who doesn't?)
Anyway, this and the Mario/Sonic thread has reminded me of a little fact. Where there are gaming crossovers, there will be people with no grasp of copyright law who assume anyone and everyone can appear in these crossovers.
I still remember all the people seriously asking for characters like Master Chief before Super Smash Bros. Brawl came out, because Snake and Sonic being in meant everybody could be in. And right now, it's a good idea to stay away from anybody discussing Marvel vs. Capcom 3.