Fred Topel over at Craveonline interviewed scriptwriter Todd Berger (of "Kung-fu Panda" fame) on a number of ongoing projects, and one of the things they discussed was Brian Henson's live-action / animation mixture "Happytime Murders".
When asked the question if they were aiming for a PG-rating Todd answered: "It is full-on R. There is swearing, there's sex, violence, murder. There's no way. Maybe with some work it could be PG-13 but as of now we've embraced the R rating."
Wowzers! Sounds like fun to say the least...
Todd says a few other things as well, but this really looks like it's shaping up to be something we haven't seen in a long time: a feature animation aimed at a mainstream adult audience. And that is cool.