Erin Moran, the actress best known for playing Joanie Cunningham on the decade-long television classic Happy Days, passed away on Saturday. The 56-year-old was found unresponsive by emergency medical technicians at her home in Indiana on Saturday afternoon. Moran became one of America's most familiar faces in 1974, playing the "Joanie," the younger sister of Ron Howard's "Richie" in the hit sitcom. Moran continued in the role in the spinoff Joanie Loves Chachie, which was cancelled after one season in 1982.