Dave, as he puts it, is an elf with no class. Between him and his partner Christmas Carol, he is the more air-headed of the two, much like how Cosmo is less intelligent than Wanda. Carol is a first-class elf, and as such, takes her work more seriously than her partner does.
Early on in the film, Dave and Carol locate Timmy Turner and tell him that Santa wants to have a word with him, due to his using his fairy family to grant everyone's Christmas wishes. They bring Timmy, along with his fairies and his girlfriend Tootie, to the North Pole and show them around Santa's workshop. After Timmy accidentally injures Santa and finds that his name being on the Naughty List prevents him from substituting for the big guy, Dave and Carol accompany his group on a death-defying journey to find Elmer the Elder Elf, the only one who can remove Timmy's name from the list.
Over the course of the movie, Dave and Carol, alongside their fellow elves, do not get along well with Cosmo, Wanda, and Poof, as they have been feuding with the fairies for centuries. The reason for this, stated by Dave at the end of the movie, is that the fairies borrowed a power drill from the elves two thousand years ago and supposedly did not return it (in actuality, Wanda states that they did return it and left it on their back porch). During the journey, despite their constant bickering with the fairy couple, Dave and Carol eventually find that they have more in common with Cosmo and Wanda than they thought. At the end of the film, Dave and Carol finally start being more friendly towards Cosmo, Wanda and Poof, thanking them for helping save Christmas.