Have any passengers crashed planes? The question Are pilots allowed to let passengers fly the plane? is interesting to read, noting that pilots are permitted to allow passengers to fly.

I recall an Air Crash Investigation episode (AFL593) where the pilot pretended to allow his son to manipulate the controls of an airliner, without realising the autopilot had been disconnected, resulting in an accident.

I'm wondering how commonplace this is? Is this an isolated incident?

On the flip-side, I've heard of at least 3 occasions where passengers have successfully landed planes, e.g:
No passengers have crashed an airplane while the pilot was letting them fly.  

In this situation, the PIC crashed the plane because he didn't do his job as the captain and final authority for the safe operation of the airplane.

Letting a passenger fly would most likely be listed as a "contributing factor" by investigators looking into an accident where this happened, but responsibility for the crash lies squarely on the PIC.