Even before the first Mamma Mia! film, starring Meryl Streep, Amanda Seyfried, Christine Baranski, Julie Walters, Pierce Brosnan, Stellan Skarsgård, and Colin Firth, James was a fan of the musical. “I saw it like ten times [in London]. I would sing it in the house all the time and my brothers would hate it and tell me to shut up,” she admitted to Fallon.

“At my mum's birthday, which was two months before I even knew a sequel was happening—before I auditioned—I was pretty drunk and I danced on the table in sparkly dungarees and sang ‘The Winner Takes It All,’” James confessed.

She also revealed that her one hang-up about starring in the project as young Donna, a younger version of Streep’s character, was the idea of taking on a role with the fingerprints of Streep. “That was the only thing that really stopped me. Who would be crazy enough to do that?”

But Streep wasn’t the only star on set. Cher takes on a role in this film, and two of ABBA’s members were on hand. “I recorded with Benny [Anderson] and Björn [Ulvaeus] from ABBA. They're total geniuses.”

In fact, at the premiere party, James was asked to sing with Benny. “Cher was at the party and there had been whispers that Cher was going to perform,” she explained. “Everyone was ushered into the room thinking Cher’s going to sing. It was me and my two dynamos, Jess [Keenan Wynn] and Alexa [Davies]. We were a bit drunk, and we just sort of sang along while Benny played ‘Mamma Mia.’”