It's hard to believe that after so many years being one of Hollywood's biggest movie stars, Leonardo DiCaprio had never lent his voice for an animated film. Alas, in these times where studios still think A-list names sell tickets, even when you can't see their pretty faces, it was only a matter of time before Leo went before the microphone to speak for a cartoon character. He'll be heard as the voice of Jack Frost in DreamWorks Animation's The Guardians, based on the upcoming series of books by children's author William Joyce (A Day with Wilbur Robinson, source of Meet the Robinsons).

The computer-animated film will be directed by Peter Ramsey, whose only known credit is the recent Monsters vs. Aliens DVD spin-off Mutant Pumpkins from Outer Space. Interestingly enough, The Guardians is also somewhat holiday-related. In addition to Jack Frost, characters include Santa Claus and the Easter Bunny, as well as the Tooth Fairy and the Sandman. The plot follows the heroes as they band together to battle the Bogeyman. Why Cupid, Baby New Year and Punxatawney Phil didn't join the group is unclear, but they all seem like weaklings in most depictions, so their reputations may have been a factor.
DiCaprio is the first actor attached to the movie, though in the past names such as Natalie Portman, Dwayne Johnson and Hugh Laurie were apparently linked to different roles, according to the film's Wikipedia page, which also has Hayden Christensen listed as Jack Frost. DiCaprio's character is also the first we've gotten a good look at, via a concept rendering, seen below.

Joyce's books, the first of which arrives a year from now, are being adapted by Pulitzer Prize-winner David Lindsay-Abaire, who scripted Fox Animation's Robots and worked on the upcoming Spider-Man 4. The Guardians is expected to hit theaters November 2, 2012.