Leaving Audience

This is when a character is doing a speech/acting/dancing/reading in front of an audience. If the subject is a bit complicated, the writers want to tell us it's complicated. And since the average guy doesn't like complicated stuff, he leaves. So you have this character on stage, reading a report about possible life on Mars, which is critical to the main plot, while random people are getting up and out of the room. Sometimes until there are only a dozen people left listening.

Sometimes done to show that the scientist is comically anti-social and doesn't have enough charisma to hold an audience, even if he's showing off alien technology that would make everyone immortal. Or possibly that his theories are so off-the-wall that they can't possibly be taken seriously--see the Stargate example below. In this latter variant the audience is usually the speaker's peers, rather than random guys, and they're leaving not because they don't understand him but because they think he's full of it, and some of them tell him so.

This trick has been done countless times in series, comics and movies.

Compare with Chirping Crickets, Long Speech Tea Time.

Anime and Manga

 * A recent chapter of Franken Fran has Fran delivering a lecture on her new process of delivering babies via metamorphosis, with the ideal that it can be used to reduce birth mortality rates among the mothers. As the other doctors flee the room in horror, we have a rare moment of Fran being brought to tears until a new doctor walks into the room to express interest.

Film

 * The movie Stargate did a very good Leaving Audience scene with Dr. Daniel Jackson explaining the vital plot point that someone other than the Egyptians (possibly aliens) built the pyramids -- and it also tells us a lot about his character in his reaction to everyone leaving.
 * Happens to Wayne Szalinski in Honey I Shrunk the Kids.
 * Happens to a lecturer on Mormonism in Around the World in Eighty Days. Thirty people show up, but after a few minutes Passepartout is the sole auditor--and then even he leaves.
 * The titular characters of The Producers wanted this to happen when they created Springtime for Hitler. The entire audience was on the verge of doing this right after the end of the opening number. Then Hitler started singing...

Western Animation

 * Road Rovers, "Still a Few Bugs in the System": The wacko of the week talks about how bugs have lived for millions of years, and people leave as he talks about humans becoming bugs to allow for longer life.
 * Happens in an episode of The Simpsons. Springfield just built a new performing arts center. The place is packed. The Springfield Philharmonic Orchestra starts into Beethoven's 5th Symphony...and after eight notes are played, everyone simultaneously stands up and makes for the door. Aside from Marge horrified to learn that the town is uncultured, Lenny declares they already have the song as a ring tone. Exaggerated when even the orchestra leaves after Marge announces that the next piece is by Phillip Glass.