ET’s Lauren Zima chats with JoJo Siwa and her dance partner, Jenna Johnson, at their rehearsal ahead of ‘Grease’ night on ‘Dancing With the Stars.’ JoJo, who has been performing in the public eye since she was a young kid, opens up about how Jenna has helped her overcome her body image struggles while working together on the show. ET also surprised the dancing duo with a very special message from Sandy herself, Olivia Newton-John.

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