The running gag is a popular hallmark of comedy television shows and movies. A running gag is an amusing situation or line that constantly reappears through the course of a movie or television series.
Running gags are often in the form of a response to commonly used words or phrases.
In Airplane!, Dr. Rumack (Leslie Nielsen) responds to sentences containing the word "surely" with "Don't call me Shirley".
In Monty Python's Flying Circus, episode 15, the constant appearances of the Spanish Inquisition. ("Nobody expects the Spanish Inquisition!")
Also in Monty Python's Flying Circus, a knight in full armour often used a rubber chicken to hit people over the head; this was used as a bridge between scenes, mainly during the first season.