Who played George Jefferson in 'The Jeffersons'?

Who played Charles Ingalls in 'Little House on the Prairie'? In which TV series is Charles Ingalls a main character? Who played Laura Ingalls in 'Little House on the Prairie'? In which TV series is Laura Ingalls a main character? Who played Vinnie Barbarino in 'Welcome Back, Kotter'? In which TV series is Vinnie Barbarino a main character? Who played Jack Tripper in 'Three's Company'? Who played Chrissy Snow in 'Three's Company'?