Revealing mistake: When Kelly goes for her commercial, you can see that there is a stocking head cover to make her appear bald.
Revealing mistake: Kelly lost all her hair as a side effect from pimple potion. You can see the lines on her forehead that show she's wearing a flesh piece covering her hair to make her look bald. The color is lighter than her face. (00:18:42)
Answer: It was one of the hoses connected to the engine, nothing specific, but to indicate that Al tampered with the vehicle.