If no one is laying on the floor, a walrus pile may be started by wrestling the victim to the ground and then shouting "Walrus pile" as normal.
Steve: "WALRUS PILE!!!"
Aaron: "Mmmmfph! Mmph!"
Daniel: "Hey Tucker did you hear how we got 10 people in on a walrus pile on top of Aaron?"
Tucker: "Yeah, I heard you made him cry. Ha ha ha!"