Roller Disco - S3-E5
Revealing mistake: When Jackie and Fez are doing their Roller Disco routine, it becomes very obvious that doubles are used for many of the routines. Fez does a lot of his own stunts but Jackie does very few. While they do a decent job of hiding the stunt doubles, there are several times when you can see the faces of the doubles and it is obvious it is not Mila Kunis or Wilmer Valderrama. And you do not need slow motion or stop action to see the difference. (00:11:10)
Revealing mistake: Hyde claims he's reading a Mad Magazine spoof of Smokey and The Bandit. Look closely at the issue, and he's actually reading a spoof of the movie Dog Day Afternoon. That and Mad Magazine didn't make any parody of Smokey and The Bandit.
Eric's Drunken Tattoo - S3-E22
Revealing mistake: In the scene where Eric tries to kick Donna's door open. When he does, he falls back and hits the wall behind him, which wobbles.
Answer: It's Ashton Kutcher's dog.