This trope is most common in musicals, but is not strictly relegated to only musical fare.
You have a happy go lucky or other highly charismatic character who is getting everyone around him/her all excited about whatever it is they're excited about.
Then there's the one character who isn't swept up. They're worried that everyone is all excited and not thinking it through. They are concerned that there's something shady under all the happy excitement. They're just grumpy and think all this excitement is too silly and twitterpated.
But as the song/scene goes on, the excitement spreads, and the enthusiasm grows. The lone holdout will find themselves going along and either catch themselves with embarrassment and stop — or will not catch themselves and end up going with the flow.
Compare with Not so Above It All
Anime and Manga
- Aversion: In Mahou Sensei Negima! Chisame when everyone is making a Hooray for [Grinding] until she starts thinking of them as friends (With the [Heroic BSOD] Chapter 176 pages 04-05.
- In Beauty and the Beast, Cogsworth is the only character who thinks that everyone else singing "Be Our Guest" and treating Belle with food behind the Beast's back is a bad idea and tries to stop them. He eventually joins in on the singing and dancing near the song's end.
- Enchanted: Giselle starts singing "That's How You Know" — Richard is embarrassed and annoyed. Then he's shocked when the local musician buskers join her. By the time Giselle has gotten most of Central Park involved, he's sarcastically playing along. By the final chorus, though, he's smiling and bobbing his head along with the tune, until he catches himself with a mortified "what the hell am I doing?!" expression.
- In Tangled, Flynn Rider watches the majority of "I've Got A Dream" sung by Rapunzel and the Snuggly Duckling thugs with a you've-got-to-be-kidding-me expression on his face. His eventual participation in the song isn't exactly voluntary — he's basically forced into participating at swordpoint after initially saying that he doesn't sing — but it is implied that he became swept up enough in the song's sentiment to respond later to a thug's exhortation to "follow your dream" with a genuinely enthusiastic "I will!" (the thug was actually addressing Rapunzel and thought that Flynn's dream sucked, but still).
- Kamina appears to have this power (as noted by the author) in DOUBLE K.
- The Shove in Unseen Academicals: a single moment where all humans are united in a single emotion (to the point of creating false memories), including the wizards unused to such emotional outbursts.
- On How I Met Your Mother Barney often gets really excited about some new thing, and will spend a lot of energy trying to get his friends to be just as psyched about it. This only works about half the time, though.
- During Season 17 of The Amazing Race, the teams had to do a Roadblock where one racer had to find a piece of fake food in a buffet full of real food. The task was set in a real restaurant in Hong Kong, with real local customers being entertained by singers on a stage. While her teammate Claire struggled through the task, Brook jumped up on the stage, started dancing, and stole attention from the singers. She got the restaurant patrons to chant Claire's name, and, when Claire finished the task, had the entire restaurant in an uproar.
- Season 21 had this happen again for another eating task, also set in China. The restaurant's patrons seemed confused at first to have all these Americans with camera crews eating hasma without using their hands, but twins Natalie & Nadiya pumped up the crowd with their Bollywood style dance, to the point that the crowd continued cheering for every team that came afterwards.