The season finale of Family Guy, "Chap Stewie," will air tonight on Fox. In "Chap Stewie," when Peter and Chris interrupt Stewie's TV time, the angry baby goes back in time to break up Peter and Lois, so he's never conceived. But instead, he is reborn into a "Downton Abbey"-esque British household. The voice cast includes Seth MacFarlane as Peter Griffin, Stewie Griffin, Brian Griffin, Quagmire, and Tom Tucker; Alex Borstein as Lois Griffin and Butch Woman; Seth Green as Chris Griffin; Mila Kunis as Meg; Mike Henry as Cleveland Brown; and Patrick Warburton as Joe. Guest voices include Cary Elwes as British Guard #1, Doctor and Valet; David Thewlis as British Father; Isaac Hempstead Wright as Aidan; Adam West as Mayor West and Rick Springfield as Himself. Family Guy, "Chap Stewie," airs Sunday, May 18 at 8:30 PM ET on Fox.