The title of this post does not refer of any propensity towards farting on the part of our puppy Rascal; he certainly does pass gas on occassion, but no more than any other dog. No, with it I mean to suggest that, at least in the bed at night, he expands to fill the space available to him. If he's up against you and you roll over away from him, he's instantly smooshed up against you again, preventing any attempt to roll back the other direction; if you curl up your legs he's into the vacated spot in a flash, and unless you want to kick him you'd better stay curled up the rest of the night. And it's not that he's moving all around: he just fills all these spaces simultaneously. It's especially amazing because he's not a particularly large dog, in the daytime.