When the puppies are pulling Jean George's sled dogs out of the water, Francois (the black husky) is on Jean George's dogs' right, while Philippe (the red husky) is on their left. However, in one screenshot, Francois and Philippe switch places. In the next shot, they have switched places back.
When Budderball is rolling in a snowball down the hill and hits the tree it's obvious that it's a toy dog that falls out of the snowball.
(At around 12 mins) When snow dogs are running with their master, the brown snow dog is running on the front right side, next shot of them the brown snow dog is running on the front left side, next shot of him he's back to running on the front right side again.
When Shasta first meets the buddies, he says he is an "Alaskan Husky" but he is really a Siberian Husky. Alaskan Huskies are more of a mutt version of Siberian huskies, but Shasta definitely looks more like a purebred Siberian, especially with his blue eyes.