Comedic themes that could be real hits in their respective genres

F’rinstance, the theme to Blazing Saddles, despite the absurdity of the title, sounds like it really could be from a legitimate Western of old. “Springtime for Hitler” from ***The Producers *** really does sound like a Broadway hit. And “Benson, Arizona” from Dark Star could actually be a C&W hit in real life.

Can you think of any others?

Which was Brooks did intentionally (and brilliantly). As described in Wikipedia:

The good-sized storyline in ENTOURAGE isn’t all that funny unless you’re already chuckling at the idea of an ‘Aquaman’ blockbuster quickly grossing a cool billion.

Musical mockumentaries are probably cheating – but if they aren’t, I’d like to single out Spinal Tap’s “Tonight I’m Gonna Rock You Tonight” and Llewyn Davis’s “Please Mr. Kennedy.”