Since the set-up or deception is generally eventually revealed to the victim, the butt of the joke is thereby made to feel foolish or victimized. Therefore there is an inherent strain of cruelty in most practical jokes. There is no clean-cut boundary between practical jokes and hooliganism, vandalism, or sadism.
A Robotic massage chair is a chair that contains internal electronic motors and gears designed to massage the person sitting in them. Most robotic massage chairs have some form of controller to vary the type, location, or intensity of massage.
In (mostly military) aircraft, the ejection seat is a system designed to rescue the pilot or other crew in an emergency. In most designs, the seat is propelled out of the aircraft by an explosive charge or rocket motor, carrying the pilot with it. The concept of an ejectable escape capsule has also been tried. Once clear of the aircraft, the ejection seat deploys a parachute, and descends safely to earth.