Just Married ... With Children - S2-E20
Other mistake: Al gets sat on by 3 heavy women. The scale says 927 pounds. 4 more women sit down and the scale says 1071. So 4 more heavy women only added 144 pounds? Impossible.
Just Married ... With Children - S2-E20
Other mistake: Al and Peg win a new Mustang in this episode. It's never seen again.
Just Married ... With Children - S2-E20
Revealing mistake: When Al spins Peg on the wheel to win the bowling ball, in the long shots, you can plainly see its not really Peg on the wheel. It's a dummy.
Just Married ... With Children - S2-E20
Factual error: In the game show near the end, when Marcy and Steve come out as Al and Peggy. When the real Al and Peggy win the car, because they used Marcy and Steve's names, the car would have never gone to the real Al and Peggy. In reality, it would have gone to Steve and Marcy because it was won under their names. Al and Peggy would not have been able to keep the car. In fact Al and Peggy would not have been allowed to be on the show at all using someone else's name.
Answer: It was one of the hoses connected to the engine, nothing specific, but to indicate that Al tampered with the vehicle.