Matthew Perry, Matt LeBlanc's co-star from Friends (1994), was considered for the lead role.
Ed watches an episode of Friends (1994), the show that made Matt LeBlanc a star. The scene he watches features Marcel, the pet monkey of one of the characters. He appeared in the first 2 seasons, and his story-lines were similar to the one in this movie.
Ed, the chimp, is actually "just a guy in a suit" (according to Matt Leblanc), with a mechanically controlled head. That head made so much noise that all the dialogue in the scenes which included the "chimp" had to be re-dubbed in post-production.