In which TV series is Arthur "Fonzie" Fonzarelli a main character?

Who played Klinger in 'M*A*S*H'? In which TV series is Klinger a main character? Who played Fred Sanford in 'Sanford and Son'? Who played Arthur "Fonzie" Fonzarelli in 'Happy Days'? Who played Richie Cunningham in 'Happy Days'? In which TV series is Richie Cunningham a main character? Who played Charles Ingalls in 'Little House on the Prairie'? In which TV series is Charles Ingalls a main character?