Continuity: When Fletch first sits on the water bed, the guitar falls from the wall. In the next shot the guitar hangs on the wall, although nobody put it back there.
Continuity: When Fletch is masquerading as the exterminator, he supposedly finds a microscopic termite. As he's showing it to the Sheriff's Deputy, the position of his hand holding the flashlight changes back and forth as the camera angle changes.
Revealing mistakes: When Fletch leans on the railing outside his 'new' house and the railing collapses, you can see that the top rail has been cleanly and evenly cut vertically so it will break away easily.
Continuity: In the biker bar scene, it's pouring rain when Fletch goes in. It's dry when they come out. Then the roads are wet again when they go riding to the train. Then, after they jump through the boxcar, it's dry again.
Continuity: When Fletch is being wheeled into the morgue by Calculus, Ben Dover removes Fletch's wristwatch and puts it on his right wrist. When Ben sits down at his desk, the watch is on his left wrist.
Continuity: Fletch attends two different tapings of the Jimmy Lee Farnsworth television show, but the announcer introduces both of them as the "4,323rd edition" of the show.
Errors in geography: During the first scene in the newsroom, as Irwin 'Fletch' Fletcher and Frank Walker walk through the office, we see a map of Long Island, New York on the wall in the background. The newsroom is supposed to be in Los Angeles, California. (The scene was filmed at Newsday's Melville, Long Island office.)
Continuity: When Fletch rides the motorcycle through the moving boxcar, the train is rolling from right to left. When the gang leader tries to jump through the first scene shows him after leaving the ramp and the train is rolling in the same direction. The next scene shows the wheel of the motorcycle coming through the side of the boxcar and after that, it shows the train rolling in the opposite direction with the wheel of the motorcycle in front of the open door. If the biker missed the door with the train moving, the wheel would be behind the door, not in front of it.