Danish (?) Flashmob

What's going on here?

Mukhtars Fødselsdag

Mukhtars Fødselsdag or Mukhtar's birthday in English. Apparently the flash mob was set up as a surprise to celebrate the driver's (Mukhtar's) birthday. It's an advert for Bedre Bustur (Better Bus ride), a campain organised by Arriva and Movia (local Danish bus companies) and aimed at making bus rides a pleasant experience.

Fieldgate gives a bit more information, but I have to admit I was a bit flummoxed by the OP because the location and purpose of the video is clearly described by the uploader.

I didn't word it well. I was interested in what they were singing. It's certainly not "Happy birthday to you." Is it a traditional birthday song?

Yes, it's Danish birthday song. First the tune, slightly false, on trumpet on the bus, and then again sang by the mob in the street.

First the tune, slightly false, on trumpet

Slightly false?!

"slightly", yet recognisable.

What are the words to the song? If you only have the name, I can look it up & let Google translate it.

If you google 'fødselsedag sang' with Danish spelling you'll surely find it.

nice video btw