There’s a trick to a dark comedy. There has to be a fundamental wrongness about the situation — else it isn’t dark — and yet there also has to be something likeable about the protagonist. Maybe it’s a genuinely good person in a bad situation. Or maybe it’s somebody who isn’t so good, but manages to be entertaining.In director Jan Egleson’s 1990 film A Shock to the System, the latter approach is taken, and a large part of its success can be put at the feet of star Michael Caine.