The New Car - S4-E6
Audio problem: When Felix and Oscar are driving around looking for a parking space, Oscar says "let's sell the car." Felix then begins talking but no audio is heard, then an overdub of him saying "Are you crazy?" which doesn't match his lips.
Continuity mistake: In the opening credits of the first season of The Odd Couple, Felix is moving in "with his childhood friend", Oscar. In a subsequent season, a storyline does a flashback to say that Felix and Oscar met when they were both jurors at a trial. Soon after, they cut the word "childhood" on most of the openings after people called the station to mention the mistake.
Continuity mistake: When Felix is shown being thrown out of his apartment and entering Oscar's apartment, the suitcase under his arm is a different color than when he is shown on the street on the way to Oscar's apartment.
Continuity mistake: When Oscar is on his way into his building, his sweat suit is perfectly clean after playing baseball. Once in the apartment he is covered in dirt.
Scrooge Gets an Oscar - S1-E12
Continuity mistake: Watch the scene when Oscar opens his mini garbage pail gift. You'll see it's completely free of the inside tissue wrapping. In the next shot when he goes to open the lid, there's a piece stuck between the lid and the base that was not there before. (00:20:40)
The New Car - S4-E6
Continuity mistake: The odd couple lived at 1049 Park Ave. But in this episode they say they live at 74th and Central Park West.