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)
Visible crew/equipment: In the film George is backing his Rolls Royce up at Hugh's place, as he's doing that the film crew's reflection can be seen on the car. (00:08:00)
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)
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)
Continuity mistake: During the seduction scene, as George and Jenny attempt to make love to Ravel's "Bolero", the record gets stuck. George throws a pillow at the record player, closing its lid and "unsticking" the record. But when George later turns off the record player, the lid is open again.
Deliberate mistake: When George spies on his hedonistic neighbor down the hill with his telescope, the telescope is always level when it actually should have been pointing downward. Same when his neighbor spied on him - his telescope was always level also when it should have pointing upward.
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.
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: 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.
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.
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.