Katy Perry Opens 'Witness' Tour With Cover of Janet Jackson Hit -- Watch!

What has Katy Perry done for Janet Jackson lately? 

The 32-year-old singer covered Jackson's 1986 classic, "What Have You Done for Me Lately," during Tuesday's opening night of Witness: The Tour in Montreal. 

Perry, who performs 20 of her greatest hits and six different costume changes during the show, donned a black-and-white number as she put her best spin on Jackson's choreography from her performance of the song at the 1987 GRAMMY awards. 

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Perry's tour was originally supposed to start on Sept. 7 in Columbus, Ohio, but was pushed back last month due to "production delays." 

"Due to unavoidable production delays, major elements of my tour stage design could not be available for me to rehearse on until this week,” Perry said in a statement at the time. “I’ll be spending the next few weeks taking the time to properly prepare the show to be an experience I am proud to share with you. I'm sorry for any inconvenience this causes, but hope everyone who sees the show will agree it was worth the wait."

See more in the video below.