Several minor traffic accidents occurred when Will Ferrell walked through the Lincoln Tunnel in his costume, because people were so surprised (and distracted from their driving) to see him wearing an elf outfit.
Director Jon Favreau used a remote control to trigger the Jack in the Box toys to get the startled reactions from Will Ferrell.
The scene when Buddy eats different candies and pastries with the spaghetti noodles had to be shot twice, because Will Ferrell vomited the first time.
The cotton balls Buddy eats while in the doctor's office were actually cotton candy that had not been dyed.
According to Will Ferrell at the movie's premiere co-star James Caan approached him and said he felt Ferrell's performance in the film was "too over the top" while they were shooting the movie. However when Caan saw the finished film, he later said he understood the energy Ferrell needed to put into his performance and later praised Ferrell saying he gave a good performance.
Ray Harryhausen: According to The Ray and Diana Harryhausen Foundation, director Jon Favreau wanted to include stop-motion segments in tribute to classic animated Christmas specials such as Rudolph the Red-Nosed Reindeer (1964). Stop-motion pioneer Ray Harryhausen was invited to record the voice of the Polar Bear Cub, one of the animals Buddy the Elf (Will Ferrell) says goodbye to when leaving the North Pole.