Quiz Whizz (1958)

Joe wins a contest and is promptly fleeced out of his winnings by some con men. When the stooges go to recover his money, the bad guys convince them that they can get rich by posing as children and becoming the wards of a millionaire. The boys go along with the plan, not realizing that the "millionaire" and his pretty niece are in on the scam and are planning to knock them off. The stooges foil the plan and recover Joe's money.