Robbie Ignacious Hilary is the son of Rudolph the Red-Nosed Reindeer and the main protagonist of the Robbie the Reindeer trilogy. He is the love interest, later boyfriend and eventual husband of Donner.
Donner first fell in love with Robbie in the first film Hooves of Fire, when he arrived at Reindeer Lodge to become the navigator for the Sleigh Team. However, Robbie was unaware of this as he was already in love with Vixen and thus, only saw Donner as a friend.
Whilst attending a party at Santa's home, Donner looks on in annoyance as Robbie is in awe of Vixen.
After Robbie left the Sleigh Team after being tricked by the team's Captain and Vixen's boyfriend Blitzen into thinking that he would slow the sleigh down, Donner finds him working at Santa's Workshop and tells him that in order to get his place back in the team, he must win a medal at The Reindeer Games. Robbie happily agrees and says he will do it for himself, his father and, to Donner's annoyance: Vixen. After convincing a former coach named Old Jingle to help train Robbie for the event called The Steeplechase, Donner helps out.
On the day of The Reindeer Games, Vixen attempts to use Robbie's crush on her to stop him taking part in the Steeplechase (as she wishes for Blitzen to win, so he gets famous and takes her out of the North Pole), however Robbie refuses and is shown to have fallen for Donner as he mumbles his words. Robbie briefly leaves the race to help Old Jingle after becoming trapped under his house after trying to push it up a hill. Robbie returns to the race and is able to catch up with Blitzen, who knocks him to the ground with a hurdle. With encouragement from Donner and Old Jingle, Robbie uses an ability called The Nose Jump to catch up with Blitzen and appears to cross the Finster line at the same time as him, before being accidentally trampled by the other competitors. Donner then comes to Robbie, who once again mumbles his words, to which Donner asks if he can't talk because he loves her or because he was just trampled by a herd of reindeer, before giving Robbie a kiss.
After Blitzen is arrested for cheating in the race by taking a drug, Robbie is made winner by default and Santa let's him borrow his new sleigh for the night. Robbie uses the sleigh to take himself and Donner on a date to the moon.
In the sequel, Legend of the Lost Tribe, Robbie becomes Donner's boyfriend and at the end of the film, during a fight against Blitzen, they get engaged. In the film, Close Encounters of the Herd Kind, the two get married after the defeat of an evil alien race called the Nargarthrons.