"I’ve got a rather large dog, actually," Sirius cuts in, "well-behaved and all, but the extra space to run would be appreciated; big dogs do need quite a bit of exercise." Remus had made jokes like that a lot, when they lived at the flat together; "oh dear, guess you haven’t gotten enough walks today", or "you’re getting restless, let’s go to the park and I’ll toss a stick around", or "I should’ve known a big dog would require this much exercise." He had even gotten a book (from... someone) about how to care for big dogs, which he enjoyed reading aloud from when Sirius was exhibiting certain "doglike" traits.