Once Upon a Time Machine is the second Easter episode of the 1987–1996 animated Teenage Mutant Ninja Turtles series. It originally aired over CBS aired on 29 March 1991, during the series fourth season. While not so Easter-themed as The Turtles and the Hare, it features the Easter Bunny Hokum Hare from "The Turtles and the Hare" assisting the turtles in preventing Shredder to time travel into the future and rule it.
Hokum Hare discovers that the Shredder is using a time train to travel to the future and become a crime lord in an era without crimes. Shredder originally proposes to travel to the year 3000, long after the Ninja Turtles have died so they won't have there for him to encounter and destroy. However, Krang makes an error in the programming of the time portal, located in a subway tunnel, and when Shredder and the mutants pass through it, they end up only in the year 2036. The Turtles and Hokum jump on the time train. When they arrive in the future they find the elder versions of themselves, who are retired. Now, the younger Turtles try to whip their older selves up into shape before the big confrontation.