Factual error: In the part where they show the sperm going to the egg, it is biologically wrong the way they show the sperm go inside the egg - only the head part of the egg enters a sperm, everything else stays on the outside and eventually dies off.

Continuity: When Mikey is talking about his diaper being wet in the crib there is a rattle to his right which appears and disappears throughout the scene.

Continuity: When Molly takes Mikey to the Chubby Charles office to meet Albert, she changes his poopy diaper and slams it down on his new desk, rendering it junk. She then puts Mikey back on the floor, but never snaps the legs on his overalls. In the next shot, you see Mikey smashing Skeletor on the floor and his snaps are done, but when Molly picks him up to leave the office, they are undone again.

Continuity: There is a car chase scene where they show him driving wearing sunglasses, then they cut back to him and he's not wearing them, then they cut back to him and he is wearing them...

Visible crew/equipment: In the scene where John Travolta is racing Kirstie Alley to the hospital, there is one shot where a camera rigging is clearly seen mounted on the hood of Travolta's taxi in the reflection of the storefront windows.