Uma Thurman and Jesse L. Martin (Law & Order) are joining in the fun for NBC's holiday special Letters to Santa -- A Muppets Christmas.

According to The Hollywood Reporter, Letters to Santa -- A Muppets Christmas is set on Christmas Eve when Kermit and company mistakenly avert three letters en route to Santa Claus, which triggers a race against time to bring a happy Christmas to the kids whose wishes were lost in the mail.

Thurman will play Joy the ticket clerk for the North Pole Airlines and is also Santa's flight attendant.

Martin will play a postal worker who stars in the opening scene of the special, doing a singing and dancing number with the muppets.

Thurman and Martin join previously cast Whoopi Goldberg, Tony Sirico and Steve Schirripa, Richard Griffiths and Madison Pettis, along with Kermit, Fozzie, Gonzo, Miss Piggy and the rest of the muppets gang.