Continuity mistake: As Kelso goes rolling by in the hall with the wheels on his shoes, you can see they are actually skates and the wheels are black. When he asks who put the tiny wheels on his shoes, the shoes are now normal and the wheels are white.
Continuity mistake: As the janitor hugs Carla, he picks her up and you see part of her hair gets caught on her cheek. When the shot changes its all suddenly pushed back. The following shot it goes back to halfway down her cheek.
Answer: Dan was drinking beer and Cox feared that Dan might get so intoxicated he would fall asleep and drown in the tub.
Mortug