"If I Was Your Girlfriend" (Prince)

Sitting in the middle of Prince's sprawling double album Sign O' The Times (1987) is the curious track "If I Was Your Girlfriend."  The Purple One wrote the song to explore his feelings of jealousy regarding his then-fiancée Susannah Melvoin's close relationship with her twin sister, Wendy Melvoin—the guitarist in Prince's backing band, The Revolution.  In short, he realized Susannah would never share the same degree of intimacy with him as she did with Wendy, and that bothered him deeply.
But instead of writing the song from a guy's point of view, he wrote it from a woman's point of view, expressing the wish that she could share the same kind of lasting bond with her boyfriend that she shared with her best girlfriend.  (It's a pretty daring exercise in psychology for a pop song.)
To take the concept even further, Prince recorded the song with sped-up vocals to sound like a woman.  He even credited his alter-ego, "Camille," for the performance instead of himself.  In fact, the song had been slated for inclusion on a full Camille album, which he ended up shelving in favor of Sign O' The Times.
I don't mean to imply that the song is just some odd curio or throwaway, though; its slinky beat, slapped bass, and soulful hook make it one of the best tracks in his entire catalog.  It's a shame it was so misinterpreted and ignored at the time of its release.