Show Stopper

A performance or performer that evokes so much applause from the audience that the show is temporarily interrupted.

For obvious reasons, this is primarily a theater and live performance trope, as static audiences can't exactly rise up and give a standing ovation in a movie theater. It can still be parodied in that context, though, as pretty much everyone knows the basic idea behind a show stopper. Indeed, such meta-awareness dates to early 20th century film, if not earlier — it's an essential part of the live performance genre. Sometimes the script might actually call for the actors to nod toward the fourth wall in thanks.

A sillier variation, often enforced by a Laugh Track, is where a single character, simply by appearing on the stage, evokes such thunderous applause from the audience that everyone has to take a break before any lines can actually be said. Note that in original theater this was still part of the point. Back then it was called a clap trap — a part of a play or a musical performance designed to evoke applause, with a pause in the action to accommodate it. Since then, the phrase has been used to mean nonsense.

This is the supertrope to Epic Song.

Examples of Show Stopper include:

Film

Austin Powers does it all the time. After doing or saying something cool, Austin turns to the audience and says, "Oh, thank you," in reply to the applause he expects.
Lampshaded in Forever Amber when the actors pause to acknowledge the entrance of King Charles II.
"The Parson's Bride" segment of the 1936 version of Show Boat, in which all the actors acknowledge the audience at their entrances and exits.

Live-Action TV

Whose Line Is It Anyway?, being performed in front of live audiences, often relies on at least one sketch being this in each performance. There's also a special game called "Show Stopping Number", which parodies this trope.
- Although the most epic one was probably Sid Caesar's guest appearance.
- Or Richard Simmons'.
The Weekenders made fun of this trope. An act in the talent show burned down the stage, and therefore stopped the show.
Kramer on Seinfeld
Fonzie on Happy Days
In Home Improvement, every time a funny is made, the Reaction Shot of (usually) a confused Tim lasts for several seconds before the laughter dies down.
Steve Urkel from Family Matters would often evoke this response upon entering the scene.
Red Dwarf has the line-delayed-by-laughter version: the Polymorph takes the form of Lister's boxer shorts, which start shrinking after he puts them on. Kryten is despeterately trying to remove them when Rimmer walks in. There's a very long pause before Rimmer makes a comment, because Chris Barrie had to wait for the audience's laughter to subside enough to be heard.
Parodied in a sketch on The Carol Burnett Show where she and Harvey Korman played famous stage actors. They would enter the scene within the scene and get tons of applause, which would always stop as soon as they acknowledged it and started to bow, creating many uncomfortable pauses.
In later seasons of Married... with Children, the entrance of nearly any major character was met with cheers and hoots from the studio audience, forcing the cast to pause for a second before continuing the scene.
In a segment of The Chaser's War on Everything, Chas "tests" whether botox/fake-tans/dyed-hair will increase his attractiveness (or rather, make him hot like Daniel Craig). He does this to only one half of his body and face, leaving the other half untouched. The utter ridiculousness of his appearance leads to continued laughter from the studio audience even when Andrew attempts to move on to the next segment of the show, eventually causing Andrew to start laughing as well and have to restart the segments introduction. See here
The three-part DCLAU Crossover "That's So Suite Life of Hannah Montana" had applause play whenever a character entered another's show.
Johnny Carson's appearance on Late Show with David Letterman.
Lenny and Squiggy's Once an Episode appearance -- always in hilarious "coincidental" response to some cue -- on Laverne and Shirley.

Professional Wresting

One time on WWE Smackdown, when Hulk Hogan returned to WWE, his applause lasted an entire TV segment (approximately 15 minutes). When they came back from commercial, the crowd was still applauding — but since it wasn't broadcast live, it could have been only a short time after they "went to break" that they stopped. (Or conversely, it could have gone on for even longer.)

Radio

I'm Sorry I Haven't a Clue: "It's now time to play the game called Mornington Crescent."

Web Original

Homestar Runner: ONION BUBS! ONIOOON BUUUUUBS!!