Ferris Bueller's Day Off (1986) - 9 major mistakes

Visible crew/equipment: When Ferris, Sloan, and Cameron pick up the Ferrari at the parking garage you can see the camera and its reflection in the window directly behind Ferris and Cameron.

Continuity: When Jeanie meets the boy at the police station, his hair changes after every cut from her to him.

Visible crew/equipment: Near the beginning of the movie there is a brief scene around the empty house. While the camera is in the kitchen you can see a reflection of one of the set guys moving in the fridge handle.

Continuity: The rear view mirror disappears when Jeanie is speeding home.

Continuity: When Ferris is kicking his shoes off at the end of the movie before jumping back into bed, he kicks his right shoe off and then he kicks the same shoe off again.

Continuity: When Ferris is about to jump in the pool to save Cameron there is a cookie floating in the water. As he jumps in it disappears.

Continuity: In the scene where Ferris is doing his dancing thingy to "Twist & Shout", there is a cop wearing a blue jacket from the street view, and then he's not wearing it in the next shot from an aerial view.

Continuity: When Mr. Rooney goes to Ferris's house he is wearing a long sleeved shirt and coat jacket.  A shot of his arm ringing the doorbell shows a bare arm with dark hair.   When they return back to a shot of Mr. Rooney, his sleeve is touching his wrist and he does not have dark hair on the back of his hand.

Continuity: At the end, Jeanie slams the kitchen door in Mr Rooney's face. Watch the pane of glass in the door. In all previous exterior views of the door, the pane is composed of about 4 horizontal pieces of glass. It is apparently a "jalousie" window that opens like a venetian blind, so there are no mouldings between each piece of glass. However, as soon as we see the inside of the door behind Jeanie, visible through the curtain is the silhouette of a "criss-cross" moulding grid, dividing the window into 9 panes of glass.