Okay, so I'm a few weeks behind, but I watched the "Bowie" episode of Flight of the Conchords last night, and musically, it's brilliant. Even better than the guest appearance by the man himself on Extras last year, I'd say.
And it really works because they don't even attempt to explain why David Bowie (well, their version of him, anyway) shows up in the episode. Bowie exists in a reality unto himself, and that's part of the joke. Total genius.
Here's Bret dreaming about "1976 David Bowie, from the Ziggy Stardust tour:"
And here's the first part of the absolutely fabulous "Bowie's In Space" music video:
My only complaint about the series is that outside of the songs, the comedy tends to be a little too broad. The gender role reversal in "Girlfriends" was hilarious, but the main characters--Jermaine, Bret, and band manager Murray--are played as complete idiots who wouldn't survive a New York minute in the real world. I don't mind that they're clueless, or naively child-like, but being so utterly vacant is starting to break the fourth wall for me.