He is voiced by Nathan Greno.
Biography from the official site
Dasher is one of the legendary eight reindeer who pull Santa's sleigh every Christmas Eve. Dasher is unflappable in his self-confidence, priding himself on his piloting skills and the extremely large amount of fur on his chest.
Dasher likes to butt antlers with his fellow reindeer to psyche himself up.
Dasher doesn’t care for peeled carrots. He likes them raw, thanks very much.
Dasher has a recurring case of Athlete’s Hoof, and has been taking advice from Dr. Autry, the Reindeer Trainer & Nutritionist, on how to best treat his ailment. Slightly embarrassed by his malady, Dasher became quite annoyed by Dancer when the latter accidentally mentioned it to the entire Sleigh Team during flying practice.
Dasher is first seen with Dancer and the rest of the sleigh team preparing to guide Santa's sleigh on Christmas Eve. The team are later contacted by Magee as they travel during a snowstorm.
After Santa is told to skip Timmy's house (due to it not being prepared), Dasher and the rest of the sleigh team turn and go a different direction. However, Wayne manages to contact Santa and convince him to come back to Timmy's house and thus, the team turn back around and manage to land on the roof, but nearly fall off, taking the sleigh with them. Luckily, Wayne and his partner Lanny are able to help in time.
Dasher is last seen with Dancer and the rest of the Santa's elves celebrating at a party.