Big Wolf on Campus (1999)

S1E19 Hair Today, Gone Tomorrow

A cool new substitute teacher arrives at school, and Tommy quickly realizes it’s Mr. Dunleavy—the very werewolf who bit him. Eager to bond with his new "dad," Tommy starts spending all his time with him. When Merton warns that Mr. Dunleavy might be dangerous, Tommy brushes it off and ignores the warning entirely.