In the 1993 film "So I Married an Axe Murderer" the main character's best friend Tony is a police officer who is unsatisfied with his career. He joined the force because he thought it would be exciting like on TV. Instead of chasing criminals and getting yelled at by his boss, he spends most days doing paperwork while his captain is very calm and kind-hearted. Tony even confides his frustrations to his captain to which the captain even responds "hey, somebody needs a hug."  

Later in the film, Tony is in his office when the Captain barges in and begins berating Tony for the way he's trying to solve a case. The Captain continues yelling and even grabs Tony by the shirt and pins him against a wall, telling him that he better not screw things up. Tony nervously agrees and exits the room. Seconds later, Tony re-enters, smiling and expresses how proud he is of his captain. The Captain, now speaking bashfully, says that the act was fun. This happens once more toward the end of the film where the captain is even seen practicing some angry lines to himself.

\-

In My Hero Academia during a rescue exercise, 2 students are teamed up against 2 other students: one pair playing the heroes while the other play the villains. Iida is a very stern but friendly young man who takes everything he does very seriously. Since he is portraying a villain, he gives himself a pep talk in order to get into the proper villain mentality. He then says out loud in an unconvincing manner, "I am... extremely evil!" Opposing student Uraraka overhears this and laughs from afar, giving away her hiding spot. 

\-

In Seinfeld, George Costanza is met with a small gang called "The Van Buren Boys" who plan to beat him up. In an attempt to avoid this, George insists he's also a member of the same gang. The gang doesn't believe this and even asks him to prove it by mugging the next person who walks by. Coincidentally the two who walk by are Jerry Seinfeld's parents, who he knows. He goes up to them while the gang watches from afar. George quietly asks for Mrs. Seinfeld's purse and says he'll give it back later. The couple is confused and instead asks about how he and his own parents have been doing lately. George then begins to shout at them and unconvincingly insist that he is "an animal." George then weakly attempts and fails to take Mrs. Seinfeld's purse. They begin to walk away with Mrs. Seinfeld telling George that he's behaving very rudely. Mr. Seinfeld also happily tells George to tell his parents hello for them. Granted, George isn't particularly a "nice" character but he's still really bad at playing a bad guy.

\-

In SpongeBob SquarePants, SpongeBob wants to get into the Salty Spitoon, which is a club exclusive to very tough and muscular members. SpongeBob makes multiple hilarious attempts to gain entry but is repeatedly denied. Later he and Patrick fake a fight so he can get in. The dialogue they exchange before the fight is super awkward with Patrick even stating while slowly reading from his hand that he is a professional kickboxer. Shortly thereafter Patrick beats himself up without SpongeBob even touching him. Although obviously an act, this was humorously enough to impress the bouncer to give SpongeBob access. This is probably one of my favorite episodes. 

[Funny Trope] Nice Characters pretending to be mean