In The Big Lebowski, there are two men with the name Jeffery Lebowski. One is an erudite millionaire, one is a complete slacker better known as "The Dude." Two goons confuse the latter for the former, peeing on the Dude's rug, which jumpstarts the rest of the movie's plot.
This is the principal plot of "Identity Thief" as a con-woman steals the identity of a man.
Probably inspired by the Molière example, the French filmmaker Francis Veber often has a character named François Pignon or François Perrin. Notably, in earlier movies, this character tended to be a Butt Monkey who was the unwitting cause of humorous calamity on others, but in more recent movies is a sympathetic "everyman" character who gets a happy ending. In fact, the word pignonisme has been adopted in the French language to reference the attitudes of the "man on the street".
"Homer Simpson" is a character from the 1939 novel The Day Of The Locust which was turned into a movie in 1975. The name is unrelated to Matt Groening's cartoon character from The Simpsons.
A multi-lingual example: 1997 saw the release of both Takeshi Kitano's film "Hana-bi" and Leonardo Pieraccioni's Italian comedy "Fuochi d'artificio", around the same time. Both titles mean "Fireworks" in their respective language, but the films couldn't be more different to one another.
Likewise, Ridley Scott's Black Rain and Shohei Imamura's Kuroi ame were both released in 1989. "Kuroi ame" means "black rain" in Japanese.
Two basset hounds named Fred: Cledus Snow's pet dog in Smokey and the Bandit and Alex Graham's comic strip pooch (currently drawn by Michael Martin and Graham's daughter Arran).
Joel Coen is half of the writing-directing team The Coen Brothers. Joel Cohen is another Hollywood writer. The name is also shared by a classical musician who uses the latter spelling.
This confusion is purportedly why Bill Murray signed on to play Garfield, confusing Cohen for Coen. Doesn't explain the sequel, though.
Don't forget Joel H. Cohen, a frequent writer for The Simpsons and Saturday Night Live.