Mac is a Serial Killer - S3-E10
Continuity mistake: When Dee is explaining that her and Dennis are going to just take the tools because her neighbor Gary is in love with her, Dee's hands are empty. When the shot switches to Dennis saying, "That works," she has a big silver wrench. (00:11:25)
Mac is a Serial Killer - S3-E10
Plot hole: Early in the episode, it is mentioned that the serial killer is murdering "Young, attractive blondes", yet at the end of the episode, when the gang finds all the severed heads in the killer's refrigerator, almost none of them are blonde or young, contradicting what had been previously established.