So, let's get this right. Mel Brooks' The Producers was a film about a play. Which was then turned into a play. That has now been filmed. Glad we got that straightened out. Here sleazy theatrical producer Max Bailystock (Lane) and meek accountant Leo Bloom (Lane) team up to deliberately produce a flop, having worked out they can make more money that way than with a success. They get the rights to a play written by loopy Nazi Franz Liebkind (Ferrell) and set about making it even worse. Naturally, all their efforts are for nothing, as the lurid exercise in bad taste proves a roaring success, which causes more problems, not least the Liebkind is now out to shoot them all for defaming his Fuehrer.
I did see the original, and about all I remember of it is Springtime for Hitler; the same is likely true of this version. That remains a masterpiece of over-the-top absurdity, though the obvious winking at the camera defuses the offensiveness: real bad taste is played dead straight [see Ilsa for details]. The rest of the film rarely reaches anything approaching such depths and is much more forgettable as a result. It's generally solid enough, with a few decent laughs: the regular film actors in the cast [Ferrell and Thurman] come over better than Lane and Broderick, who still seem to think they're on Broadway. They also brought in the stage director to handle the film and that was likely a mistake: Phantom of the Opera definitely benefited from having someone behind the camera who had a clue. I can't help thinking things would have been much improved if they'd brought in the South Park creators to do the songs.