An expression used by a character in numerous episodes of a show. Merely uttering this phrase in the office will key others in to 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.

text via tvtropes.org