When angsty young singer Alanis Morissette landed Dave Navarro and Flea to help record the backing music for what would become her first hit single, 'You Oughta Know,' it was a major coup. Alanis was virtually unknown at the time -- outside a couple relatively obscure albums and her run on the '80s Nickelodeon show 'You Can't Do That on Television,' that is -- and Dave and Flea were A-list rockers with the Red Hot Chili Peppers. But despite the serious star power involved, their contribution was done on the down-low -- and it certainly wasn't the first time such a high-profile guest spot had been kept a secret. Suckers for trivia, we've teamed up with our friends at Ultimate Classic Rock to put together a list of 20 Rock Songs With Secret Guests -- tunes that feature notable guest appearances that might totally surprise you. Check them out.

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