(Strip Number 574, Original Publication Date, 17 March 1984)
Panel 1: As he staggers back into bed, John tells Elly that he's oiled Humphrey's exercise wheel.
Panel 2: Elly tells a scowling John "Good! As long as he's quiet, he'll be no trouble at all."
Panel 3: We then look in on Humphrey as he roots around in his bedding.
Panel 4: For some reason (or, since his brain is the size of a lentil, for no reason at all), he kicks a lot of his bedding onto the floor.
Summary: As I said, the description in the catalog implies that he did so because he misses the noise. This doesn't make sense because he's a hamster. He can no more plot to screw with Elly and John than he can survive Lizzie's great big hug.