The TVTropes Trope Finder is where you can come to ask questions like "Do we have this one?" and "What's the trope about...?" Trying to rediscover a long lost show or other medium but need a little help? Head to Media Finder and try your luck there. Want to propose a new trope? You should be over at You Know, That Thing Where.
A variation of Mugging the Monster- the character is socially or politically powerful rather than physically powerful.
Compare its subtrope Robbing the Mob Bank- the mob's bank might be easy to rob (After all, Who Would Be Stupid Enough? to rob the mob's bank), it's the consequences that come with it that are the problem.
2 is more of a Bavarian Fire Drill overlapping with invoked Mugging The Monster; by claiming to be a teacher he not only gets rid of the harassers, he scares them badly enough to deter them from questioning his story.
Edited by Scorpion451
1 sounds like Unintentionally Notorious Crime (second paragraph)
Mugging the Monster
Bully sees a victim who the bully assumes will be weak and helpless, and starts harassing him. Bully then has an OH CRAP moment when he discover that he picked the WRONG person to pick on. A few examples that come to mind:
1. The West Wing: Some drunk frat guys harass a girl they meet at a bar and the guy she is with. They discover the girl they are harassing is te president's daughter, and the Secret Service quickly deals with them.
2. Catch Me If You Can: Some high school bullies harass a young-looking man, who turns out to be their teacher. Of course, he wasn't really a teacher, but they still had the OH CRAP moment because they thought he was.
3. Chiefs: A corrupt police officer in a small southern town in the 1960s pulls over a black man and starts harassing him for no good reason. That black man turned out to be the new Chief of Police.