Green Day had been booked to perform on 'Jimmy Kimmel Live' on Wednesday night, but with frontman Billie Joe Armstrong in rehab, Alanis Morissette stepped in and treated viewers to a dark cover of the classic Green Day hit 'Basket Case.'

Morissette's performance turned the humorous, self-deprecating pop-punk gem into a moody, dramatic cry for help. Morissette sounded like she was channeling a lost soul when she gently sang the hook, "Sometimes I give myself the creeps / Sometimes my mind plays tricks on me / It all keeps adding up / I think I'm cracking up / Am I just paranoid? / Or am I stoned?"

The singer was initially backed up only by piano, but drums and guitars crept in as the song moved along. As she finished, Morissette said, "We love you, Billie Joe." 'Basket Case' was a No. 1 rock single for Green Day in 1994 from the album 'Dookie' and remains one of their most popular recordings.

In addition to honoring Green Day, Morissette performed 'Guardian,' the lead single from her latest album, 'Havoc and Bright Lights,' which debuted at No. 5 upon its release last month. The singer-songwriter is touring the U.S. now.

Watch Alanis Morissette Perform 'Guardian' on Jimmy Kimmel