***In the film Felix is a tv newswriter; in the tv series he’s a commercial photographer.
*** In the film Felix spells his last name Ungar; in the series it is Unger.
***In a later telefilm Felix’s daughter is Hannah; in the series it’s Edna.
*** In the film Oscar has 2 kids; in the series he has none.
***In the film Felix’s wife is Frances; in the series it’s Gloria. Blanche is Oscar’s ex in both film & series.
***In the film Felix’s wife throws him out in July; in the series he was tossed on November 13.
***In the film Felix’s brother lives in Buffalo & is a doctor; in the series his brother lives in Buffalo, but runs a bubble gum company.
***At the end of the film Oscar throws Felix out of his apartment; in the show Felix is still living there.
***In the film the boys have dated the Pigeon sisters regularly, but in the series opening episode they appear to be dating them for the 1st time. But this is SOP in tv shows made from films, as the 1st episodes often recap the film’s basic premises.
***In the film only Oscar is divorced, Felix is merely separated; in the series both men are divorcees.

http://www.cosmoetica.com/b107-des62.htm

Then you have to wonder about the play.

I saw the film in its entirety once and the main difference that I noticed had to do with Oscar. In the film he had children and in the series he did not.