Christina Aguilera crashes Hayden Panettiere's "Lip Sync Battle"

First it was Beyonce, and now Christina Aguilera is the latest diva to crash the stage at "Lip Sync Battle."

Actress Hayden Panettiere guest-starred on the show and performed the 2001 hit "Lady Marmalade." Panettiere mimicked Aguilera's throwback look from the music video, complete with a huge blonde wig and a corset and gloves.

But the real surprise came when Aguilera joined Panettiere on stage to perform a few lines from the song. Unlike Panettiere, though, Aguilera is not lip syncing -- and the diva definitely still has her pipes.

Watch the teaser below.