What show did Scott Baio star in before "Charles in Charge"?

The answer is: Happy Days. At 16, Baio landed the role of Chachi Arcola, the cousin of the Fonz from Happy Days. He reprised the role in the spin-off, Joanie Loves Chachi, which was sadly cancelled after just 17 episodes. But not to fret, Baio would soon get another leading TV role and boy would he take charge of it.Source