Any bit of humor
which relies primarily or exclusively on visual
s, rather than wordplay
, sound effects
, etc. Can include, but is not usually limited to, a visual pun
A classic cartoon sight gag involves moving the stripe in the center of the road so that someone will follow it into a wall. A similar sight gag is to paint a tunnel or door onto a wall, which first works for the intended sucker and then reverts to trompe l'oeil for the trickster.
The sight gag is generally distinguished from physical comedy by being surreal or impossible. There is no clearly defined boundary, however; the mirror gag in the Marx Brothers' Duck Soup, which has been copied by many later comedy writers, is both inspired physical comedy and a brilliant sight gag.