In the scene where Richard and Nikki are in Teddy's (Nikki's ex-boyfriend) apartment retrieving her belongings, Richard and Nikki begin singing Biz Markie's Just a Friend as she zips up her sweater but when Teddy arrives at the apartment her sweater is unzipped. As the camera continues back and forth, the sweater goes from fully zipped to half zipped to fully unzipped and back.
Richard Cooper's (Chris Rock's) arm position between shots in the ambulance: At first we see a paramedic trying to hold Rock down as the other paramedic prepares to operate on him and Rock's arms up trying to struggle with him. In the next shot, his arms are down by his sides with no struggle, then immediately in the next shot he is being held down by that same paramedic and has his arms up struggling once again.
After Richard takes the Viagra and is on the phone with George, Brenda comes in and catches him. After Richard tells George "I gotta go," he never really hangs up the phone, he only places it down. Also, Brenda never actually dials 9-1-1.