First let’s get a couple of questions cleared up, though, the answers are pretty apparent. First, did your friends sit on the clutch pedal while opening up the engine, trying to make the rear wheels smoke? And, was there a whole bunch of smoke coming out of the front end when he finished?
With those questions asked, let’s see if we can’t find the answer. The answer is likely yes to the first one and yes to the second. It sounds like your friend has fried the clutch plate (also called a clutch disk) by holding the clutch at what is called the “friction point,” causing all sorts of smoke to build up. Honestly, it really looks super to have the wheels smoking as the engine on the WRX winds up, but, what you are really doing is causing one humungeous slippage to occur, frying the surface of the clutch plate. It is also possible that in addition to the clutch plate the throw-out bearing has been roached pretty well, too as the constant pressure on the clutch may have damaged it the bearing. It is also possible that when the clutch plate was fried, the pressure plate — the device that actually provides the pressure on the back of the clutch plate — was also damaged. One more thing that may have happened is that face of the engine flywheel — the device that takes the engine’s power and transfers it to the transmission — may also have been damaged.
If, as is probably the case, the clutch plate, pressure plate, throw-out bearing and the flywheel were damaged while your friend was busily creating havoc with your transmission and your WRX’s tires, you are looking at some major repairs as the transmission will have to be dropped so that the engine flywheel can be dropped and replaced. Further, the clutch plate, pressure plate and throw-out bearing will have to be replaced as well, making this a rather expensive mistake. You are looking at the better part of $2,000 in repairs when all the bills are counted.