Forced perspective can be made more believable when environmental conditions obscure the difference in perspective. For example, the final scene of the famous movie Casablanca takes place at an airport in the middle of a storm, although the entire scene was shot in a studio. This was accomplished by using a painted backdrop of an aircraft, which was “serviced” by dwarfs standing next to the backdrop. A downpour (created in-studio) draws much of the viewer’s attention away from the backdrop and extras, making the simulated perspective less noticeable.
As with many film genre and effects, forced perspective can be used to visual-comedy effect. Typically, an object or character is portrayed in a scene, its size defined by its surroundings. A character then interacts with the object or character, in the process showing that the viewer has been fooled and there is forced perspective in use.
An example used for comic effect can be found in the slapstick comedy Top Secret! in a scene which appears to begin as a close up of a ringing phone with the characters in the distance. However when the character walks up to the phone (towards the camera) and picks it up it becomes apparent that the phone is extremely oversized instead of being close to the camera. Another scene in the same movie begins with a closeup of a wristwatch. The next cut shows that the character actually has a gargantuan wristwatch.