How can one cat make so much noise?

[Karena]

My bedroom is above my office where I work all morning. Simba loves my bedroom and often goes up there to play. When I'm working downstairs it sounds like a herd of elephants running around up there and I often think it's the dogs so I go up to take a look at what is going on and all I see is one little cat sitting on the bed looking completely innocent so I go downstairs again only to hear it start up again. Goodness only knows what he does when my back is turned but it sounds like he is running around the room at great speed, onto the bed and off again, but I have yet to catch him in the act