What song did Will Ferrell sing in the bedroom in the movie?

In the movie "Elf," Will Ferrell's character, Buddy, sings "Baby, It's Cold Outside" in the bedroom. He performs this duet with Zooey Deschanel's character, Jovie, showcasing his quirky charm and enthusiasm for the holiday spirit. The scene is memorable for its lightheartedness and humor, highlighting Buddy's childlike innocence.