Rent Full Moon High (1981)

It's circa 1960, and high school football star Tony (Adam Arkin) is living with his conservative CIA agent father, Colonel William Walker (Ed McMahon). Their relationship takes a turn for the worse when Tony accompanies the Colonel on a trip to Romania - where he is promptly bitten by a werewolf, transforming the teenager into a monster. Upon returning to America, Tony's newfound curse causes his behaviour to spiral out of control and he is forced to leave his small town behind. He eventually returns twenty years later - but a marked side effect of his curse is that he doesn't look a dav older than when he left. No matter how much the world has changed. Tony is forever a teenage werewolf...