A wall wobbles when Harry bumps into it as he grapples with Red's henchman, indicating that it's a set rather than a real hospital room.
When Duke's owner takes him back, he decides to give Harry another German Shepherd Dog, but it's clearly the same dog, its fur has the same color pattern. Even though Duke gets into the SUV and the "other dog" gets out in the same shot, there must have been someone inside who slipped a different collar on it (notice how the owner pauses for a couple of seconds before he lets the other dog out)