Dancing on a Bus

A song sequence that frequently appears in Bollywood films. Inspired by his beautiful surroundings, or by a beautiful love interest, the character sings a rousing anthem to demonstrate either his patriotism or his love, while defying the laws of gravity.

The vehicle needn't be a bus; it could be on any vehicle. Trains are just as likely.

Examples of Dancing on a Bus include:

Film - Bollywood

A notable example is the "Chaiyya Chaiyya" opening song from Dil Se, where the characters dance on top of a moving train.
Makes an appearance in Salaam-E-Ishq, in the song "Dil Kya Kare".
Shows up in Veer-Zaara, when Veer sings "Aisa Des Hai Mera".
In the Hindi movie Rab Ne Bana Di Jodi Surinder dances on top of a little yellow car while singing his signature song, Haule Haule. He also sings and dances on top of a bed.

Film - Others

Not a Bollywood film, but a variant of this does happen in Across the Universe
A non-Bollywood example: The film of the musical of the film Hairspray features a musical number sung and danced, in part, on a school bus.
"The Trolley Song" from Meet Me in St. Louis.
"Man on the Flying Trapeze" from It Happened One Night.
Star Spangled Rhythm has a cartoonish sequence in which Betty Hutton sings "I'm Doin' It For Defense" while struggling to stay on a jeep.
Austin Powers dances with Miss Kensington on a double-decker bus as Burt Bacharach plays the piano.
In At The Circus, Groucho sings "Lydia the Tattooed Lady" in a train car.
In A Hard Day's Night, The Beatles sing "I Should Have Known Better" in a baggage car on a train.

Music Videos

The music video for Bjork's "Big Time Sensuality" shows Bjork singing and dancing in the bed of a truck slowly driving in New York City.

Theatre

In Bells Are Ringing, "Hello, Hello There" builds into a big dance number on a subway car.