One of our heroes is taking a stay in the hospital, and her friends are by the bedside. As they're talking, in walks a scrub-clad individual, usually with a syringe, and with nothing but murder on the brain.
Now, unless it's a singularly nightmarish hospital, this "nurse" is not actually on the company payroll. Indeed, much of the time, the medical staff put a stop to it by recognizing that fact. (Perhaps villains should employ down-on-their-luck doctors as evil mooks
.) At other times, the heroes visiting their incapacitated comrade will have been sufficiently paranoid to order that no unauthorized visits be made - whether that's typically in their character or not.
In any case, playing nurse to kill someone almost never pans out. It's one of the more disposable villain roles out there.
- In Sailor Moon: Another Story, a youma tries killing Hotaru while she's overcome with dark energy. Haruka, being the only character cynical enough to prepare for such an eventuality, has, of course, prepared.
- The first person to try and assassinate Baron Wulfenbach in the Mechanicsburg Hospital plays it cool slightly better than most when questioned. Slightly.
- In The Dark Knight, the Joker dresses up as a nurse (with hella scary lipstick) in order to blow up a hospital.