Mickey Mouse, Donald Duck, and Goofy are working together at a service station. When cigar-smoking customer Peg-leg Pete arrives, they happily salute him and offer their services. Pete rudely explains that his car is making a squeaking sound (to the tune of "Yankee Doodle"). He gives them a 10-minute deadline to fix his car "or else". He signals with his fingers that he will cut their throats. He then leaves the service station.
Suitably intimidated, the three men get to work. They start dismantling the car to search for their problem, while the tune of "Yankee Doodle" never stops. In their haste, the trio makes several errors and its members suffer through a series of accidents. Mickey eventually discovers that the tune was not coming from the car parts. A tiny grasshopper was stuck within Pete's car, and kept playing the tune with its legs.
The trio try to kill the grasshopper with their tools, but only manage to accidentally destroy parts of the car. Mickey then realizes that their deadline is ending, and signals to Donald and Goofy that they must re-assemble the car. Their haste causes a new series of accidents, and they keep getting in each other's way.
By the time Pete arrives, the car has been re-assembled. But nobody has bothered to check if everything works properly. Pete enters the car and starts the engine. The car has problems starting, and the trio tiptoe away from Pete. Then the car starts functioning as a torture device, trapping Pete within.
The car eventually dismantles itself, with only the engine remaining in operation. Four legs emerge from the engine, and it starts acting like an out-of-control animal. It chases Pete, attacking his buttocks. Pete starts howling in pain and trying to escape, as the film ends.
