Like the rest of the songs in the 2005 film and musical The Producers
, "I Wanna Be A Producer" was written by Mel Brooks.
According to the programme for the 2005 Theatre Royal Drury Lane production, it takes place in the offices of Whitehall & Marks where it is performed by Leo and the accountants. Leo Bloom is theatrical producer Max Bialystock's accountant, and along with him the lead character in the show.
The song speaks for itself, Leo wants to be a producer, and is now on his way to becoming one.