Time Travel Episode

Basically, an episode whose plot revolves around time travel. Maybe the villian wants to remove the hero from history. Maybe the resident Gadgeteer Genius wants to see the tech of the future.

Groundhog Day Loops don't really qualify, since in that case the time travel is reset at the end.

In some cases, the time travel is a Framing Device for a Recap Episode, or for giving a character's origins.

See also Time Travel, Time Travel Tropes, Groundhog Day Loop.

Anime and Manga

 * Pokémon 4 Ever is a textbook example; Celebe's powers even include time travel.

Western Animation

 * Freakazoid had an episode where the titular hero prevented the attack on Pearl Harbor.
 * The Fairly OddParents had two episodes where Timmy went back in time, first to keep his dad from winning a trophy, and next to make Mr. Crocker less miserable. Both backfired horribly.
 * In the Underdog story "Simon Says No Thanksgiving", Simon Barsinister and Cad went back to the 1620s to prevent the first Thanksgiving from taking place. Underdog and Sweet Polly followed them to keep history on track.
 * In the second-season Pac-Man episode "Journey into the Pac-Past", P.J. turned Pac-Man's clothes washer into a time machine.
 * Futurama loves using this theme. Episodes include: "Roswell That Ends Well", "Time Keeps On Slippin", "Bender's Big Score" and "The Late Phillip J. Fry".
 * The My Little Pony Friendship Is Magic episode Its About Time.