Allegedly Stephin Merritt had been reading Ulysses, and considering how writers objectify women in metaphors. In the lyrics, he celebrates, mocks, and critiques song similes, adopting "an exaggeratedly sexist, male point of view. It's a lot of baggage for one song," he acknowledges, "but that's part of why it's funny" [source].
LD Beghtol adds:
When I first heard this, I was sure people would attack Stephin for being sexist, which of course neither he nor the song is at all. Also the song Queen of the Savages gave me pause. Happily everyone got the jokes and no-one so far as we know was offended.
Stephin cites surrealist poetry as one of his 'touchstones' for his wilder metaphors such as 'A pretty girl is like a minstrel show' [source]. (The Magnetic Fields took their name from André Breton and Philippe Soupaultís Les Champs Magnetiques [source], though Stephin says that this is "not a reference in the sense that it helps people understand the band better" [source].)