Kristen Bell makes high school prom dreams come true on 'Jimmy Kimmel Live'

The actress helped an audience member receive a unique "promposal."

— -- Kristen Bell filled in for Jimmy Kimmel as host of his show last night, helping a pair of high schoolers make a prom connection in the process.

The actress called two supposedly random studio audience members down to the stage, dressed them in costumes from her hit film "Frozen," and told them the first one to go out onto the street and find a man in a Kristoff costume would win a prize.

After they left, Bell informed the audience that one of the girls was an actress. The other -- Sarah -- was bringing back Kristoff. Little did she know that one of her high school friends, Michael, was in the costume ready to ask her to prom.

"Sarah, there's something I wanted to ask you but I didn't know the words, so Kristen Bell is going to help me," Michael said after revealing himself.

Bell then broke into song to the tune of "Frozen's" famous "Do You Wanna Build a Snowman" with lyrics changed to encourage Sarah to say "yes." She accepted, prompting confetti to explode from the stage and cheers to erupt from the audience. Bell then said the couple would be receiving some prom gifts from her, including a tuxedo rental, a stretch limousine and a "glam session" for Sarah.