Continuity mistake: In the episode where Fiona is being harassed by Craig's wife, she's talking to Debbie about having a "birthday party." Debbie says her birthday is in October. In episode 4-8 when Debbie is looking at her losing virginity calendar, her birthday is marked as being in July. And fast forward to season 7 when Monica returns and gets Franny back. She says she hasn't been that happy since the summer Debbie was born, to which Debbie replies that her birthday is in December.
Continuity mistake: After Fiona's return back home from the club where she's worked as a waitress, the blackish strips on her cheeks turn from partially rubbed off (justified by her wiping the tears) to perfectly fine a moment later, then change several more times during her discussion with Lip. (00:38:35 - 00:39:35)
Continuity mistake: When Monica and Frank are driving in the car with Liam, the Crawford Power Plant can be seen just behind the car. At this point, they have crossed the Stevenson Expressway and they are heading south down Pulaski. However, in the scene where they stop the car and argue, as Monica drives away, the Crawford Power Plant can be seen on the left, right ahead of them. (00:13:40 - 00:14:50)
Continuity mistake: A call comes through the police dispatch radio of a kid stealing from a liquor store and the address of the store is broadcasted as "44100 Western Ave", but when Carl and the lady cop enter the liquor store from the outside, the address above the store reads "2420."
Continuity mistake: Frank's bruise on his left eye (a black eye) grows larger when he tries to get the man on the forklift's attention. Earlier in the episode the bruise is smaller. Later in the episode the bruise returns to the same size it was before.