I found this on Youtube while I was searching for Donny and Marie Osmond clips:

It’s Olivia Newton-John and Donny Osmond singing You’re the One That I Want from Grease. It sounds like they changed the melody a little bit. Maybe it was done to better match Donny’s range? Regardless, I think Donny does a great job. He would have made a great Danny! I read somewhere that Marie Osmond was the first choice for Sandy. What a missed opportunity!