The couple earned a standing ovation from the crowd with their take on “Good Morning” from Singin’ in the Rain – and were awarded straight 10s from the judges.
The dance was made popular by Gene Kelly, Debbie Reynolds and Donald O’Connor in the 1952 film.
“I actually danced with Gene Kelly, and I’d be happy to dance with you any time,” said guest judge Olivia Newton-John, who worked with the legendary dancer in 1980’s Xanadu.
An emotional Grammer ran up to the judge’s table to embrace Newton-John, and after getting straight 10s, he gave thanks to his pro.
“Thank you for my partner Allison for choreographing everything, and Gene’s the man,” said Andy.
Backstage, he explained how studying the late dancer had affected him.
“It feels like connecting with a really important artist from the past. I just felt like I was really getting to know someone new as a performer,” he told PEOPLE. “I’m going to take a lot of things I learned from this guy and use it in my career.”
Dancing with the Stars airs Mondays (8 p.m. ET) on ABC.