Stupidity: Mrs. Doubtfire used the bathroom without first locking the door, enabling Chris (or anyone else) to walk in on her. A man who is dressed as a woman and doesn't want anyone to find out would make sure the bathroom door was closed and LOCKED. (01:07:09)
Suggested correction: Daniel is in his own house, and he may be used to using the bathroom without locking the door. Besides, he probably only thought he was going to be in there for a short time.
Stupidity: Dr. Cocteau's choice to unleash an enhanced Simon Phoenix without any way to restrain him is incredibly reckless and stupid. Even if Simon were to kill Eager Friendly, in the best case situation, you'd still have a madman with total computer access, martial arts knowledge, etc., that you would have no way to rein in. Sure, he can't kill Dr. Cocteau, but what would stop him from say, holding the city hostage or something? Why not add in a kill code or something to keep him in check?
Suggested correction: Who says he didn't? Cocteau has put in mental conditioning compelling Phoenix to kill Edgar Friendly and make him unable to kill Cocteau. Who says he hasn't put in something that makes him kill himself after the deed is done? Or perhaps paralyze him so he can be put back on ice. It's just that Cocteau didn't count on the fact that his henchmen could kill him. He doesn't care about how dangerous he is, not until he has done the deed.
Dr. Cocteau is a narcissistic egomaniac type that would see himself as a king or a god, even. And Simon is making him very angry. He even tells Simon, "you're beginning to be more trouble than you're worth..." Someone with an ego like Cocteau wouldn't stand for Simon's antics for very long. And would happily enjoy putting Simon back in his place by shocking, paralyzing, etc.
But he first needs him to kill Friendly. Until he does that, he'll let him play. He still sees no danger to himself.
Stupidity: There is no way Mr. Mertyle did not hear the fence in his backyard crash to the ground; there's also a likely chance he could hear his dog crying and Smalls saying the dog is hurt. Even if he could ignore the sounds of other attempts to try to get the ball back; with the fence coming down where his dog lives and the chances of an injured pet it seems far too unlikely he wouldn't have rushed straight to the backyard hearing this.