Fonz and the gang end up in dinosaur times. Richie and Ralph get kidnapped by cave-people, and Ralph is made king. There is absolutely no reason why King Ralph should be worried.
Fonzie is pulled out of the time machine and materializes in the palace of the evil Ming Fu in Ancient China. Ming Fu finds out about the time machine and seeks it out.
Heading back to Milwaukee 1957 in less than 5 minutes, an unseen vampire materializes on the ship and zaps the controls landing the gang in Transylvania, spookiness ensues.
In 1692, Fonz and the gang end up in Salem for the Witch Trials and are up against both the Judge, falsely accusing witches, but also the Witch of Salem, crashing ships on the rocks.
Cupcake finally lands the gang in 1957, but instead of Milwaukee, they landed in the Amazon Jungle, where they run afoul of a civilization of Amazon Women.
The Time Machine lands in medieval times where it is turned into a tree by Merlin the magician. The Dark Knight kidnaps young King Arthur so he can claim Camelot for himself. So, Fonzie takes Arthurs place in a joust.
It's 3057, exactly 1100 years into the Happy Day's gang future. Civilization is split up into humans living above ground and Krolacks living underground. Unfortunately Richie and Ralph end up on the Krolacks' workforce.