Production on the second series of Lead Balloon was briefly halted by a gun shot outside the flat the crew were filming in. Because the shot was captured by the production's microphones police took their footage away to examine. This turned out to be embarrassing for Jack Dee because, having not realised that it really was a gun shot outside, he had ad-libbed a bullet hitting him on the camera.
Source: Jack Dee on Friday Night with Jonathan Ross
The mis-spelling of "balloon" on the green folder during the Lead Balloon opening titles was a genuine mistake by director Alex Hardcastle. It was decided to keep the mistake and thus the second "L" that was added as an afterthought has gone on to become the show's official logo.
The first episode of Lead Balloon achieved what was, at the time, the highest ratings for a comedy on BBC Four.
The title of the show is a reference to the expression "to go down like a lead balloon", meaning to be received badly by an audience.
A non-broadcast Lead Balloon pilot was made before the series was commissioned. The scene in episode 1.5 which features Omid Djalili as a dry cleaner was taken from this pilot.
Working titles for the show included Shit Sandwich and Thank Your Lucky Stars.