From the guest and character list for the April 14 episode of Family Guy, it looks like Peter is going to go to several alternate states, including the environment of King Of The Hill, where it appears Mike Judge is doing a voice cameo as Hank Hill. Here's how FOX describes the episode, with some images following below:
PETER GOES INTO THE WILD ON AN ALL-NEW EPISODE OF "FAMILY GUY" SUNDAY, APRIL 14, ON FOX
Featuring an AMERICAN DAD cold open and "King of the Hill" opening credits
Bill Maher ("Real Time with Bill Maher") Makes Guest-Voice Cameo
When Peter, Quagmire and Joe fly on a private plane to Canada, they crash in the middle of the wilderness, far from civilization. Peter is chosen to find help, but ends up going missing for two months, only to be found as a feral creature with no ability to communicate intelligently. The Griffins must find a way to bring back Peter to his old self in the all-new "Bigfat" episode of FAMILY GUY airing Sunday, April 14 (9:00-9:30 PM ET/PT) on FOX. (FG-1015) (TV-14 D, L, S, V)
Voice Cast: Seth MacFarlane as Peter Griffin, Stewie Griffin, Brian Griffin, Quagmire, Charlotte Rae, Inspector Gadget, Pope, Roger, Stan Smith and Tom Hanks; Alex Borstein as Lois Griffin and Wife; Seth Green as Chris Griffin; Mila Kunis as Meg; Mike Henry as Cleveland Brown, Consuela and Pilot; and Patrick Warburton as Joe.
Guest Voice Cast: Wendy Schaal as Francine Smith; Mike Judge as Hank Hill; Bill Maher as Himself.
Here are some pics: