Big Momma puts duct tape on her neck when she is in the kitchen with everyone else. Moments later when she answers the door, the duct tape is gone.
When Big Momma goes downtown with Sherry, the car is parked with the top down as Lester comes up to them. When Sherry heads across the street and Big Momma walks away to head to the self-defense class, the car is seen in the background with the top up.
Malcolm's earring(s) wanders between takes, from right to left ear and from both ears to none.
When Malcolm is talking to Sherry before going fishing, he is wearing an earring in his right ear. In the next scene at the lake he is not wearing the earring.
Near the end, when Malcolm discovers the money in the trunk, Sherry walks in and he slams the trunk, throwing a pile of toys on top of the money. In the very next shot when he opens the trunk to show her the money there are no toys inside.
When Malcolm is wrestling with Nolan at the self-defense class, his shoes make squeaks like he is on a basketball court, but they are both on mats the entire time.
After Malcolm is done delivering Rita's baby, there are no tools and there is not enough time to cut the umbilical cord, which obviously has been cut.
During the scene where Sherry gets in the bed with Big Momma(Malcom) and they go to sleep , he didn't have his mask on. The next morning however, When he wakes up with John staring at him, his mask is on. (Although he may have waited for Sherry to go to sleep to put it on, as John asks him if he's been putting on his make up in the dark).
In the scene where the other woman meet up with Big Momma (Malcolm) and tell her she is losing weight , you can clearly tell that she is wearing a fat suit under her dress when she starts dancing.
The cameraman is reflected in the mirror when Malcolm is preparing Momma's mask.
In addition to the placement of the necklace, the simple fact that Malcolm was wearing the necklace in front of Sherry is a huge error. The necklace belonged to Big Momma. Sherry should have noticed this.