Catch Phrase
Clash of the Catchphrases!

Robin: Holy cow!
Batgirl: You just had to say that.
The New Batman Adventures, "Critters"

An expression used by a character in numerous episodes of a show. Merely uttering this phrase in the office will key others into the character you're referring to. For a line to be a catchphrase, it should be always the same, and not just catchy.

Note: To be a catchphrase, the phrase must be repeated multiple times — just because something is the most memorable line of a movie does not make it a catchphrase unless it is said more than once.

If the character has a Badass Creed, that will probably double as a catch phrase.

Beam Me Up, Scotty! is a false or oft-misquoted catchphrase. When the audience adopts a character's line as a catchphrase, then we get Memetic Mutation.

A Super Trope to:

Compare Arc Words, One-Liner, Other Stock Phrases, Word Power.

Contrast with Author Catchphrase, which is when a phrase is recycled across unrelated works by the same author/actor/creator.

Not to be confused with the gameshow Catchphrase, which was just named for this trope.