Continuity mistake: When George arrives at his hedonistic neighbor's house to join the orgy, he pulls into the driveway with the driver's side window of his loaner car rolled down. He gets out and goes immediately into the house, leaving the window down. A few minutes later he runs back to the car and gets in, the window is now closed. (00:48:58 - 00:51:15)
Revealing mistake: After the waitress brings George his fresh cup of hot coffee, he immediate takes a sip, and it spills down his chin from being induced by dental anesthesia, instead of actually burning him.
Revealing mistake: When the dentist aims the syringe into the right side of George's mouth, to apparently inject the anesthetic, the needle sticks the dentist's finger instead of into George's gums.
Other mistake: There is no tea or any other liquid that spills out from the overturned kettle and cups, when Mrs. Kissell 'drops' the serving tray on the Reverend's coffee table.
Revealing mistake: George's hedonistic neighbor lives just down the rolling hill from his house. Yet George drives half-way around the coast to pay him a visit.
Visible crew/equipment: The camera crew is quite visible in the window reflection during "happy birthday" (00:02:14)
Visible crew/equipment: The boom tip is visible at the beginning, when the guests yell "surprise!" (00:02:15)
Continuity mistake: Dudley Moore is driving through Beverly Hills and all the trees have leaves on them, but right after he sees Bo Derek and starts following her car, the trees are suddenly bare. (00:10:30)
Other mistake: George's hedonistic neighbor lives practically across the other side of the yard, but George drives clear around the coastline into an adjoining neighborhood to pay him a visit.