Adventure Time - Finn the Human & Jake the Dog (S05E01&02)

Finn and Jake chase The Lich through a dimensional portal where they meet Prismo, a wish granter, who tells them that the Lich wished for the extinction of all life. This leads Finn to wish that the Lich "never even ever existed." Finn is then warped to an alternate timeline, where he is a normal human living with his family and his dog, Jake on a farm.