My worst simulator nightmare is to do a check ride with an examiner who is prone to introducing bizarre and ridiculous scenarios.
As a pilot under check, I've suffered under (thankfully only a few) such goons. As an Instructor / Examiner, and particularly with a trainee approaching final Command check-out, I've found no trouble in increasing the complexity and difficulty level
a little, and, with a level of difficulty a little beyond what could be reasonably expected in the real world handled satisfactorily, given them the "thumbs up".
With the trainee having met a fair and reasonable standard at a slightly increased level of difficulty, I'm happy to call it a day. Some trainees have asked for a little more practice with the thermostat wound up, and I've carefully agreed to their request, being ever cautious not to approach the point where an already proven good standard with the trainee's confidence in good order, can now be totally shattered if the level of difficulty is taken ridiculously far.
I could recount the worst (ridiculous) multiple failure scenario thrown at me by one of the "goons", but I won't, someone might use it against the innocent.
Regards,
Old Smokey