1. HAPPY DAYS (1974-84) -- Baio's Charles "Chachi" Arcola was introduced in the 1977 season as Fonzie's cousin and eventually became a regular cast member. At first, he belonged to a local gang, but he soon morphed into a clean-cut young man and married his longtime girlfriend, Joanie Cunningham (Erin Moran), in the show's final episode.
2. BLANSKY'S BEAUTIES (1977) -- Nancy Walker starred in this sitcom as the manager of a troupe of Las Vegas showgirls. Baio was Anthony DeLuca, her 12-going-on-30 nephew.
3. WHO'S WATCHING THE KIDS (1978) -- In this sitcom, he played Frankie "The Fox" Vitola, a 15-going-on-30 kid sharing a Las Vegas apartment with his 9-year-old sister and two older sisters, who worked as showgirls. It was gone after three months. (And yes, it does sound like "Blansky's Beauties" part deux, doesn't it?)
4. JOANIE LOVES CHACHI (1982-83) -- Near the end of "Happy Days," the two characters were spun off into their own short-lived, Chicago-based sitcom. But after it failed to click with viewers, J&C both returned to the mother ship.
5. CHARLES IN CHARGE (1984-85; 1987-90) -- Baio played a "manny" who helped a couple care for their three hyperactive children. The show lasted only one season on network TV but found new life as a first-run syndication series for three seasons.