In season one, episode two, "A Family Vacation", Harold McFly (Marty's ancestor in the Middle Ages) and his love, Jennivere, decide to move to Ireland "to raise generations of McFlys". The family stays in Ireland until the 1880s, when Seamus and Maggie McFly move to Hill Valley in "Back to the Future Part III (1990)."
Phew! That was a close one! If it weren't for lightning power, Marty would have been trapped in 1955 forever, or at least until 1956.
In the episode "Back to the Future: Hill Valley Brown-Out (1992)", Doc's shirt changes from purple, to white, to purple again.
After the credits, Biff Tannen appears and makes a comment/joke about the episode. For example, the episode that involves baseball has Biff saying "Hey butt-head, how do you hold a baseball bat? By its wings! Ha ha ha". Then Biff holds a real bat by its wings which ends up biting him and ending that segment.