Robby the Robot was the breakout star of the 1956 film Forbidden Planet, with his winning good looks (which include “sax valves” and “gyroscopes”) and his sarcastic dialog (Altaira: “Robby, I must have a new dress, right away.” Robby: “Again?”). And now Robby — who cost $100,000 back in 1956 — is up for auction.