Does this really count? I don’t even know if you can accurately say that the Catwoman in that movie is the same character as…well, pretty much ANY Batman Catwoman, on TV, in comic books, in cartoons or in movies.
Alfred Hitchcock introduced the character of Charters and Caldecott in his film The Lady Vanishes, with Naughton Wayne and Basil Radford appearing as comic Englishmen who were constantly talking about the cricket results. The two characters appeared in a series of films after that and eventually was turned into a BBC TV series.
I don’t know if they’re still going to go through with it but they were going to make a Les Grossman movie which was Tom Cruise’s character from Tropic Thunder.
How about Evan Almighty as a spinoff of Bruce Almighty?
Well “Egg and I” did have Ma and Pa in it, so in some sense it was the first of the series, but Ma and Pa were not the main characters at all in “Egg and I”.