Juxtaposition Gag

The Random House Dictionary defines juxtaposition "as an act or instance of placing close together or side by side, esp. for comparison or contrast."

Many comedy writers, however, define juxtaposition as "two completely unrelated things being put together, just to see what could happen." A Juxtaposition Gag is when a character or object is placed in a normally unrelated situation or genre for the sake of a joke.

Common features of a Juxtaposition Gag are extremely obvious anachronisms (Abraham Lincoln, ASTRONAUT) or flat-out contradictory concepts (The Grim Reaper, M.D.), but any two things that are sufficiently distinct from each other can suffice.

Monty Python's Flying Circus

 * Argument Clinic
 * Bruce Sketch / Philosopher's Song
 * Ministry of Silly Walks
 * Really Camp Army Parade
 * Self Defense Against Fresh Fruit

The State

 * Taco Mail
 * Slash Infestation, in which a home is plagued by the guitarist Slash. Another home at the end of the sketch is infested with Fleas.

That Mitchell and Webb Look

 * A post-apocalyptic quiz show
 * Sir Digby Chicken Caesar: A tramp who thinks he is some sort of Sherlock Holmes figure out to save the world.

The Tonight Show

 * Some jokes on the Jay Leno "Headlines" special come from this sort of thing. Sometimes, two ads with incompatible content are placed by each other, or two ads with pictures are placed together and create improbable anatomy. Other times, the headline of one article is next to a picture from a different news story altogether, with unfortunate implications.