Season 11, Episode 17
Bart gets a glimpse of what his future will look like in 30 years time when an Indian chief (the manager of the casino Bart is ejected from) performs a kind of futuristic ritual in front of him.
Probably one of the worst episodes in the history of the series, an opinion which is backed up by several fans and critics alike.
The title of this episode is a reference to the film Back To The Future.
See here for more details.
Notes & Screenshots: Lord Heath