Visible crew/equipment: After he gets beaten up by his father, Ricky looks in the mirror. On the left edge you can see a bit of the camera, then it moves away.
Revealing mistake: In the scene when Ricky's father rushes to his room and punches him, Ricky is bleeding before he is hit.
Continuity mistake: After Lester throws the pillow, it bounces off the couch and lands in the chair. In the next shot it's gone, but reappears in the following shot.
Continuity mistake: In the scene where Ricky's dad is driving him to school, if you look closely in the background, they drive by the same houses twice.
Continuity mistake: The interior layout of the Burnham's house does not match the exterior of the house. This is illustrated in the scene in which Jane comes inside after Ricky is taping her for the first time. She walks in the front door and goes directly into the dining room to peer out of one of the two side windows. If the interior of the house matched the exterior, she would not have been able to peer through those windows because they would not have existed. Instead, the garage would be there. (While there may be a window on that side of the dining room that does face out near the garage - extended external views of the house from that side are not plentiful in the film - there are still not two windows which face out in that direction. The garage would block one.)
Continuity mistake: When Lester is drinking from the blender in the kitchen, the amount changes the wrong way. First it's half full, then a third full, then half full again.
Continuity mistake: When Ricky comes home and starts to watch TV with his parents, on close up shots of the TV there are pictures and a vase on top of it, but when they show shots of Ricky and his parents, they mysteriously vanish.
Continuity mistake: When Lester is talking about the car he's just bought, the beer on the table has its label facing the camera. On the reverse shots, it's still facing the camera. The label doesn't wrap round - later on we see that there's one front label and nothing on the back.
Continuity mistake: When Caroline is cleaning the house she is trying to sell, she's in the kitchen cleaning the counter tops. The layout is her cleaning the breakfast bar counter and the sink is behind her to the left of her. When she takes a buyer through, the kitchen layout is exactly the opposite. If you look at the breakfast bar counter top, the sink is now on the right side. Also, you'll notice the "wall" to the left of the counter top now is pushed back a little - almost like they didn't align it correctly when they put it in for shooting.
Continuity mistake: When Lester is drinking from the blender in the kitchen, the bottles in front of the kitchen window are rearranged in between the shots.
Continuity mistake: During the night out at the estate agent's party, and back at the house that same night when drinking root beer in the kitchen, Kevin Spacey is wearing a t-shirt under his shirt. After hearing his daughter and friend talking about him working out he goes to the garage, finds his weights and takes his shirt off, but there is now nothing underneath.
Continuity mistake: When Lester is jogging towards Ricky and his father, you can see the hose on the ground. It first shows the hose stretched out across the lawn, then it shows the hose sort of coiled.
Continuity mistake: At the end, when Carolyn pulls over to the side of the road in the rain, the first shot shows her windshield wipers going, then in the close-up from outside, they are not, then from the inside of the van, they are going again.
Continuity mistake: When Lester returns from a jog after embarking on a fitness spree, it can be seen that the sweat pattern changes on his shirt in the scenes following the jog. They go from long and thick to long and thin to short and thick etc.
Continuity mistake: In the scene where Lester is telling Carolyn and Janie that he quit his job if you watch Carolyn's drink you see that it changes drastically from shot to shot, between having lots of ice, not that much ice, being quite full, not as full, etc. And she never even takes a sip.
Continuity mistake: When Carolyn calls Lester and Jane out whilst honking the horn, the shot changes from her to the house several times. Each time the shot is facing the house the side mirror is flapped in and while facing her it isn't. Additionally, in the same scene when Lester comes out, his briefcase opens and his cellphone falls out toward the car out of reach, when he picks it up again it's right next to him.
Continuity mistake: In the kitchen near the end of the film when Angela asks Lester if he's been working out, there is no sweat on his arm in four successive medium shots. When she touches the arm in the close-up, it is glistening wet.