Before Santa lets Fred wear his suit after he gets injured, Fred was wearing the Santa costume that he was supposed to wear to the party. But at the end when Santa got his Suit back, Fred was wearing his regular Clothes.
While walking home from work, Fred is singing a song. He stops to help some kids build a snowman & places his turtle shell helmet on top. He then jumps on a sled & speeds off towards his home. As he walks into his house, his helmet is somehow back on his head. Dino tackles him & the helmet is gone.
It is somewhat illogical that a family existing in prehistory should celebrate an event which took place within recorded history.