Continuity mistake: When Malcolm is trying to get the TV back to the channel he was watching, he picks up a big remote and finds the channel which the video camera feed is on, but the remote he is holding on the TV is a smaller one. It then cuts back to Malcolm who is moving his hand away from the remote he just put down and it's the bigger one again.
Continuity mistake: In the scene where Lois finds out about Francis escaping, there are three orange mugs hanging from a rack by the phone. When Lois reaches for the phone to call the police, she makes the middle one start swinging. She and Hal sit down, and the end mug has moved from the rack into a box on the kitchen counter. Also, the mugs are hanging still. Towards the end of the scene, the "fallen" mug is back on the rack, and the middle mug is swinging again.
Continuity mistake: When Malcolm goes into the classroom and gives his teacher a hamburger she eats about half of the burger really quickly but in the next shot of the hamburger there appear to be only a few bites taken.
Revealing mistake: At the end, Malcolm speaks to camera with several children moving in the background. One boy doesn't know where or when to move and he tries to speak to someone off camera. In the end he gives up, shrugs his shoulders and walks off.
Plot hole: In this episode Dewey tells Francis that their aunt died from a cat eating her face (or something involving a cat mutilating her face) and we find out this is how she really did die. But then why would it be an open-casket if her face was destroyed?
Suggested correction: Morticians can do fantastic work - this is very common.
Continuity mistake: When Julie passes through the kitchen to get Malcolm, Dewey and Egg are in there cleaning the floor they have suds all over the floor, When Julie runs back through after seeing Malcolm in his underwear she slides across the floor, The floor is still completely covered in suds but when she gets up if you look in the background you see the floor with hardly any suds anywhere. She could not have soaked up all the suds when she slid across.
Continuity mistake: When Lois is in the bath tub soaking after getting upset about the family wanting to go to the funeral. Dewey comes in and ask for juice. When they are on Lois(front view) the suds barely come to the top of her breast. When the show Dewey (side view of Lois) The suds are all the way up to her shoulder.
Continuity mistake: When Lois is packing lunch in the blue cooler her hands go from on the side of the cooler to down by her waist in one frame to the next. No time for her to move it.
Continuity mistake: When we see Dewey's friend at the table eating cereal he is eating cereal and the bowl is full of milk. In the next shot the bowl is full of cereal and there is barely any milk.
Continuity mistake: Hal speaks about having held Malcolm the moment he was born. But in the Season 2 episode "Flashback" not only was he not there for his birth, he didn't hold him immediately, instead he talked to Lois.
The Bots and the Bees - S1-E14
Continuity mistake: In the scene where Malcolm and the Krelboynes are talking and watching Robots after the opening credits. There is a blue schoolbag on the table but after it is gone, but when we see the table again the schoolbag is there again.
Visible crew/equipment: You can see the crew right after the intro. (00:01:00)
Visible crew/equipment: After the theme song ends it starts with Lois just finishing shaving Hal's back. Off to the side you can see the crew kneeling down.
Continuity mistake: While Dewey stands on the table, Mrs. White (Bea Arthur) dips her finger in the bowl of chocolate and draws a mustache with it on Dewey. In the following shots the chocolate on Dewey's face differs.
Continuity mistake: When Malcolm and Reese talk about April at the water park, there's a girl with a blue shirt and a towel tied around the pelvis who passes behind Malcolm twice in two different shots.
Audio problem: Near the end when the family have got back in the car Malcolm says something like "who would have thought a traffic jam could be so cool, we should do this again". Near the end of the sentence we can see Malcolm's mouth and it isn't moving.
Halloween Approximately - S2-E2
Continuity mistake: When Francis walks into the boy's room the calendar says September 2000. In the next shot it changes to October 2000. After that Reece says "No, it really is the 31st" he flips up the September page of the calendar to October. (00:06:15 - 00:07:15)
Halloween Approximately - S2-E2
Other mistake: In the scene where boys are loading eggs into their slingshots, one of the eggs misses and falls on the roof, but doesn't break. A real egg would have broken.
Visible crew/equipment: When Lois gets in the car after she gets offended by the fact that everyone in the family forgot her birthday, you can see a cameraman with the camera reflected on the rear window when she leaves. (00:10:15)
