eter has a vestigial twin growing of his neck, and he has surgery to remove it and have it become a separate entity.
Seth MacFarlane Peter Griffin / Brian Griffin / Stewie Griffin / Glenn Quagmire / Tom Tucker / God / Kool-Aid Guy (voice)
Alex Borstein Lois Griffin (voice)
Mila Kunis Meg Griffin (voice)
Seth Green Chris Griffin (voice)