Factual error: When Felix and Oscar are on the plane and Oscar goes to sit next to Felice, the pilot says they will be landing in twenty minutes. This cant be as the police sheriff said the flight would take forty minutes. I don't think Oscar was in the bathroom for twenty minutes or the seatbelt sign wasn't on for twenty minutes either.
Continuity mistake: In the final scene when Oscar introduces Felix to his card playing buddies, watch carefully at the guy in the toupee. Between shots he has his sandwich in one hand and then hes reaching for it and then its just sitting there. This happens about three times.
Revealing mistake: When Oscar and Felix are driving on the highway, you can see the passing cars waving to the camera.
Revealing mistake: When the guy is dead in the car you can see his eyes blinking while he dead (you have to look really hard).
Continuity mistake: When Oscar and Felix are driving along the highway when the camera changes back and forth from Felix and Oscar Felix's tie goes from being under the seat belt to over the seat belt, this happens a few times.
Oscar Madison: Was it San Marino?
Felix Ungar: Not San Marino, maybe San Quentino.
Oscar Madison: Not San Quentino, San Sorina.
Felix Ungar: No not San Sorina.
Oscar Madison: San Mateo. San Clemente. Roberto Clemente.
Felix Ungar: Sancho Pancho. Pancho Gonzales.
Oscar Madison: Ferrando Lamas, Ricardo Montalban.
Felix Ungar: Ricky Ricardo.