In this case, Wolf_Bassist is very much on target. It has to do with billiards (pool). That is the meaning of the reference.

Well, here`s what I made of it----

When they throw snow at Balto, Steele happens to kick up a rock that hits Balto`s side, the motion causing him to slam into the trash barrels.

They all know that Balto`s half wolf, but Nikki makes a joke out of it that his Wolfie DNA is in his side xD Considering what he said, they might also think that wolves are clumsy, and Balto brought out his wolf side when he made an epic fail against the trash can.
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One time, I was shooting my neighbors with my brother`s Nerf Guns, and I hit my neighbor in his side, causing him to jitter off a few paces. I turned to my friend, who has seen Balto, and whispered, "Guess he`s half wolf in the side pocket there" and she cracked up xD My neighbor got mad and ran home in the rain xD

Does this help? That`s MY theory.

~Blue

Have you ever played billiards before? Or heard the phrase "8 ball in the corner pocket"? It's kind of along those lines. On a billiards/pool table, there are six pockets: four corner pockets, and two side pockets on each of the two longer sides of the rectangular table.