Looking murderous, the small, filthy boy keeps climbing on top of things and leaping off them - as though he's trying to fly. Only when he hits the ground, he growls. Or maybe he'll eventually curl up into a ball and cry.
Scenario Two
Peter found paste. Ooey, gooey, sticky paste. And he's walking around sticking things to... things. Leaves to windows. Paper to trees. Sticks to EVERYTHING. He even tried to stick himself to a wall! And when he got tired of that, well, the paste was rather tasty, so he sits down in the middle of the road to eat.
Scenario Three
If he can't have a real sword, Peter will make do with a fake one. A stick. OK, it's not perfect, but he's doing the best he can, sneaking around one of the parks and jumping out at unsuspecting people, challenging them to a fight. Or fighting trees.