wiki link on Sheldon
The genius behind Danny Thomas, The Andy Griffith Show, The Dick Van Dyke show & I Spy was an unforgettable character actor as well. He was best as the recurring 'racetrack tout' on The Jack Benny Program who would always pop up and try to talk Jack out of whatever he was doing.
Some stills of Sheldon from "It's a Wonderful Life':
'Alright you two pixies....'