Moonspear and it has to grow!

His eyes were glued to the stone, all busied with studying the smooth, very satisfying roll of it with or without his sister's presence--which he remained largely oblivious to in favor of the roundness. Only when she made her bid for the stick did it get him to pick his head up, though she was already poking at him by the time he did. "AY," he barked in protest, then whipped his rump around away from her and the poker.

The game of it registered a few seconds later. Something about sight of the twig in her teeth and not his anymore riled it out of him, and her playful growls egged him on too. He yapped again, patted the ground with his forepaws, then tried to go after the stick himself to snatch it back.