THE MISHEARD:

But Janet's up herself

The story:

I first heard the song playing Grand Theft Auto: Vice City at my sisters boyfriends house as a kid, and I knew Michael Jackson has a sister named Janet because she was recently on the news for the 'wardrobe malfunction'. I still don't get how I mixed the lyrics up!

I realized I was wrong with the lyrics when I was singing karaoke one day in music class with a friend, then when the lyrics came up on the screen, realized that I had got them wrong (I sang them correctly though, not my misheard way). Nothing too embarrassing.