During an interview on Talksport, Doc Brown revealed that a lot of the scenes had improv involved, and the scene where David (Ricky Gervais) is talking with the waitress, most of that was un-scripted. You'll notice Doc Brown hiding his face in his hoodie, this is to cover up his laugh and breaking character, due to the nature of David's comments.
Although David Brent does some driving in the movie, Ricky Gervais who plays Brent admitted he can't actually drive in real life.
When David Brent leaves his office to go on tour, an instrumental version of 'Handbags and Gladrags' plays during the scene. This was the theme tune to The Office (UK).
The song "Don't cry, it's Christmas" has been performed before in a previous podcast, The Podfather Christmas Special in 2001, by Ricky Gervais to Karl Pilkington and Stephen Merchant. Although the lyrics has been altered a little for the movie, it is the same song.
Ricky Gervais has set some live David Brent and Foregone Conclusion concerts to promote the film.