Or maybe — going back a little further in the past — you were shocked to see Eddie Murphy and Michael Jackson team up for "Whatzupwitu."
Perhaps you could not have predicted in a million years that Lady Gaga would record an entire album and tour with then-88-year-old crooning legend Tony Bennett.
Or maybe it was the song "FourFiveSeconds" — where Rihanna teamed up with Kanye and Paul McCartney — that had you going, "Wait, WHO is on the track?!"
Now it's your turn! Share your favorite totally unexpected musical collaboration in the comments (and why it was so unexpected) and it could be featured in a future BuzzFeed Community post!