S4E1 : Roswell That Ends Well

The combined explosions of a supernova and Fry putting metal in the microwave hurtle the Planet Express crew back in time to 1947. They land at Roswell, New Mexico, where a shattered Bender is mistaken for UFO debris, Zoidberg is taken in for an alien autopsy, and Fry accidentally kills his grandfather, Enis, in a nuclear explosion.