The Fonz and the Happy Days Gang

The Vampire Strikes Back (1x7)

: 20, 1980

Unknowingly aided by Count Dracula, the gang's time machine winds up back to their present time of 1957, but not in Milwaukee. They end up in Transylvania, where they meet the count at his castle and have to overcome various horrors in order to escape -- one of which has a scared boy Ralph turning into a savage werewolf.