A large portion of the original footage (including the wedding itself) was ruined by an airport x-ray machine. The scenes had to be re-shot, when additional funds had been raised to do so, some months later.
In the taxi, a sign reading "CNG" is visible on the back window. This means that the car uses Compressed Natural Gas, otherwise known as methane. Delhi regulations require all taxis to run on CNG because it creates less air pollution than gasoline or diesel.
In one scene, Deubey-ji is on a scaffolding and speaking on the phone. He climbs around and has an amusing conversation which concludes with him noting that the signal was better on the ground then on the scaffold. The entire scene, with its intricate monologue and movement, was improvised by Vijay Raaz, the actor who played Dubey. Source: Director Mira Nair in a talk at Emory University.