Dexter loves his 'Jump-a-roo'. It is a bizarre combination of hula hoop/discotheque/hovercraft/mother ship. It makes him bounce up and down like a crazy-thing and squeal with delight. It is one of the few places to put him - to leave him momentarily unattended - that he will not attempt to roll off, crawl off, or generally escape from.
It is mental.