Continuity mistake: When the Tarantula is put on Hal at the zoo, the shot is only of a yellow shirt with the tarantula crawling on it. When the shot changes to where they show the whole Hal, you can easily tell that the tarantula is fake - it is larger than it was and is in a different spot on Hal's shirt.
Humilithon - S4-E2
Continuity mistake: When Hal starts to fight with Lionel with the mop at the school when Hal turns his back you can see it is wet from the mop a few scenes before he hit them and then the frame before Lionel strikes Hal with the mop his shirt is dry again. (00:17:05)
Plot hole: Hal says that his father was never there when he got dumped. But in episode 7, "Francis Escapes" Hal tells Francis he's never been dumped.
Stupid Girl - S4-E4
Visible crew/equipment: When Hal is driving the steamroller at night alone in the car park - just before Dewey shows up - in the first shot there is a crewmen standing smiling in shorts to the side of the roller who then slowly walks out of view.
Factual error: The supposed "Amazing Spider-Man 14" that is featured is actually a copy of "Amazing Spider-Man 351". Craig calls it a 1993 reprint of 14, yet 351 is actually from 1991.
Continuity mistake: In the scene where Lois and the boys are in the clothing store, Lois piles a bunch of clothes in Reese's arms. The clothes change in his arms from shot to shot.
Long Drive - S4-E11
Visible crew/equipment: When Lois is yelling at the boys there is a camera visible on the left side of the frame. (00:01:40)
Kicked Out - S4-E12
Continuity mistake: Malcolm's seat belt changes from on to off the first scene with him and his mom in the car. When it's a shot from the front it's on, but when it's a shot from the side (from the driver's/mom side) you can see that the part of the seat belt that's going across is now behind Malcolm, instead of on him like it was a second ago. This changes back and forth.
Kicked Out - S4-E12
Plot hole: Malcolm mentions how his parents would flip if they knew he was still dating his lying girlfriend. But in the episode before (while in the car with Lois, at the end) he mentions how his girlfriend has him guessing what she wants to do. The way he says it, makes it known that he is still dating her. He says it in present tense. Therefore, they already know for sure, from his own mouth.
Continuity mistake: In the escape scene when Hal runs out the store his boss presses a button to lower the shutters. This causes the pencils to fall out of the cup but in the next shot the pencils are back in the cup and roll off the table into the fan.
Continuity mistake: When Lois and Hal work to draw up their will and then argue about Francis, Lois' hair changes repeatedly when the camera angles continually change.
Continuity mistake: This mistake happens in the scene where Dewey bumps his head. In one shot, Lois puts her hand on Dewey's shoulder, and in the next shot, her hand is on his chest.
Answer: Francis is only allowed to talk on the phone at school for three minutes a day. I think the code gives him free access to talk to his girlfriend.