Who knew Avril Lavinge was a Ke$ha fan? The 26-year-old punk princess performed the Blow singer's hit song Tik Tok while stopping by BBC Radio 1's Live Lounge.

Avril, who was there to promote her new album Goodbye Lullaby, tweeted the following after the performance:

    “Thank you to my little black stars for being up so bright and early with me to support the #Goodbye Lullaby release."

Also in the mood to sing someone else's song ... Katy Perry. While on her California Dreams Tour, Russell Brand's wife covered Lady Gaga's Born This Way. Love this acoustic version!

See Avril's newest video for "What The Hell" ... after the jump.