Sirius-as-Padfoot is dogging it around the Barge to see if there are animals in need of assistance. When he finds someone, he switches to Sirius to open doors or lift tiny animals from crevices or whatever else needs done.

He's bounding down a corridor near the kitchens because running is fun when he sees Parker. He slides to a halt and gapes at her, as best a dog can gape.

"Parker?" No one swears like Parker after all. He tilts his dog head to one side. "What the hell are you? A monkey?"