When in the park (with the kids and the snow), one of the kids tramples on some snow which appears to slide along the ground, like a rug/piece of cloth.
Shortly after halfway through when Drake/Santa is in the playground with the kids, on of the kids goes down the slide and moves the fake snow rug at the bottom when he lands.
When Drake Hunter is walking down the sidewalk with Marge the evening he is no longer Santa. Marge's heel sticks in the snow and it lifts the snow showing it is fake.