Kristen Bell helped a lovestruck teen invite his sweetheart to prom by staging an adorable Frozen-themed game while hosting Jimmy Kimmel Live! on Thursday (04May17).

The actress plucked high school student Sarah out of the studio audience and sent her out onto Hollywood Boulevard, where the Kimmel show studio is based, to find a man dressed up as Frozen character Kristoff.

The teenager, who was dressed as Bell's Frozen character Anna, found the guy and dragged him back into the studio, hoping to win a prize.

But when her Kristoff removed his costume head she realized the kid underneath was her trophy.

School pal Michael arranged the surprise 'promposal' with Bell, who serenaded Sarah with a reworked version of Frozen tune Do You Want to Build a Snowman, asking her to be Michael's prom date.

The excited high schooler said yes.

Kimmel has been asking his famous friends to fill in for him this week as he takes paternity leave to care for his baby son, Billy, who recently underwent heart surgery.