Showstopper
WordNet
noun
(1) Something that is strikingly attractive or has great popular appeal
"She has a show-stopper of a smile"
"The brilliant orange flowers against the green foliage were a showstopper"
(2) An act so striking or impressive that the show must be delayed until the audience quiets down
WiktionaryText
Noun
- A performance or segment of a theatrical production that induces a positive reaction strong enough to pause the production.
- Any impediment that prevents all further progress.