catchphrase
A short, memorable saying people repeat and recognize easily.
A catchphrase is a memorable phrase or expression that someone uses repeatedly until it becomes associated with them. When a character in a TV show says the same funny line in every episode, that's their catchphrase. Homer Simpson's frustrated “D'oh!” and Bugs Bunny's casual “What's up, Doc?” are famous catchphrases that audiences instantly recognize.
Catchphrases work because repetition makes them stick in people's minds. A comedian might develop a catchphrase that becomes part of their act, or a sports announcer might use the same exciting phrase whenever something dramatic happens. Sometimes friends develop catchphrases within their group, special expressions that mean something to them.
Politicians often use catchphrases in their campaigns, hoping voters will remember and repeat them.
While catchphrases can be fun and memorable, using them too often can make someone sound unoriginal or annoying, like they're not thinking of fresh things to say. The best catchphrases feel natural and capture something true about the person or character using them.