Over the ‘Rainbow’: Ben Platt wows crowd with surprise guest Kacey Musgraves to open Broadway residency

Dear Ben Platt, you can invite Kacey Musgraves to share the stage anytime.

The Tony-winning star of “Dear Evan Hansen” brought out the Grammy golden girl as his surprise guest on Tuesday’s opening night of his 18-show residency at Broadway’s historic Palace Theatre — which also served as the unveiling of the renovated venue.

Platt — who will have a different special guest every show in the limited-engagement run through June 15 — said that Musgraves was “the very first person that popped into my mind [that] has got to do my opening” before he introduced the country-pop singer.

“I admire her so much as an artist,” he continued. “Her songwriting has inspired me endlessly. She is so unapologetically herself. She is liberal in a space that is really not liberal, which is really incredible … And she is a dear friend. And I cannot believe that she came here, took a plane and is doing this for me. It’s the nicest thing anyone’s ever done for me.”

After Musgraves, 35, made her entrance to the delight of the crowd, she heaped praise on Platt. “Does he not sound f—king perfect?” she said.

Then Platt, 30, shared how Musgraves’ song “Rainbow” — from her beloved 2018 album “Golden Hour” — comforted him in darkest days of the pandemic. “I sang it and listened to it ad nauseum,” he said.

And of course, the two had no choice but to duet on the song, bringing the audience to their feet with their heartfelt harmonies — and giving Platt an “out of body” experience on his big night.

But that wasn’t the only “Rainbow” of the evening: Platt closed the night with a stunning rendition of “Over the Rainbow” — the signature song of his idol Judy Garland, who famously performed at the Palace in her career.

“I was very in love with Judy Garland from a very young age,” he said. “I was obsessed with ‘The Wizard of Oz’ and Dorothy and spent a lot of my childhood dressed Dorothy and just watching ‘Wizard of Oz’ after school. And I think I loved her both as that character and as a singer and a performer, and then also kind of subconsciously, as this amazing queer icon.”

Platt also paid homage to Garland’s daughter, Liza Minnelli — another legendary Palace performer. Camping it up in a fabulous dressing gown, he belted out the “Cabaret” classic “Maybe This Time.”

And Platt took time to honor the other Palace icons whose spirits were in the house — from Josephine Baker and Harry Belafonte to Bette Midler. “We welcome back all of the ghosts,” he said.

“I was very scared when the opportunity first arose, and I was looking at that list,” he said. “I felt very scared and unworthy, which I still do. But I think what I really tried to glean from that series of people … they all are so deeply and unapologetically themselves.”

Platt also performed songs from his new album “Honeymind,” which drops on Friday. His third studio LP finds the singer exploring queer love, including his relationship with his fiancé Noah Galvin — the subject of the folky ballad “Before I Knew You.”

“I wrote this song about sort of, you know, realizing that this person had been such a wonderful friend to me for so long and had already been in my life,” he said. “And right in front of my nose was the love of my life. And it’s a wonderful thing to realize.”