cobra starship did a version of this... [YOUTUBE]http://www.youtube.com/watch?v=jvVYYWCtsXQ&feature=related[/YOUTUBE]
the first video is actually Katy Perry's voice but slowed down to sound deeper, then they just synced in the words to change the gender of some of the words from "her" to "him" and so on. It's not hard to do if you have garage band or some audio editing software.