The tag line of something such as a television commercial or a joke is the phrase that comes at the end and is meant to be amusing or easy to remember.
tag line in American English
1.
the last line or lines of an actor's speech, as at his or her exit or at a curtain
2.
slogan (sense 2) slogan (sense 3)
: also written ˈtagˌlinenoun
Examples of 'tag line' in a sentence
tag line
The tag line was: `Take the worry out of monthly bills with Home Finance.
Stuart Harrison BETTER THAN THIS (2002)
'I am writing,' said Andrew,'the tag line for next year's big film, actually.