When reviewing a script with his agent at the beginning of the movie, Kit says that the letter K appears 1,456 times in the script, which is perfectly divisible by 3, meaning that KKK appears 486 times. 1,456 is not exactly divisible by 3. 1,458, however, is, and gives the stated division result of 486.
When Bowfinger leaves Carol, who is in makeup across the street from the coffee shop, here is a woman who is walking down the street away from them. She stops, looks over her shoulder at Bowfinger and then realizes he's moving and starts walking again.
When Bowfinger is in the bedroom with Daisy, counting his money, the picture behind the bed changes angle between shots (the first part of the scene was re-shot months after principal photography had finished, to include a shot of the table set for two).
Bowfinger takes off his fake pony tail and puts it in his left coat pocket before going into the restaurant. When he pulls out his business card and gives it to Jerry Renfro, he puts his hand in his right pocket, and the fake pony tail is attached to his card.
When the 2 cops pull over Kit's Mercedes, the driver exits and draws his weapon, then from another angle he's back behind the wheel, only to return to have his weapon drawn again a couple seconds later.
When Kit cannot be found, Bowfinger decides to take on a double to fill in. Although he says that they'll shoot him from the rear so it won't be obvious it isn't Kit, the first scene involves Jiff running across a highway, directly towards the camera.