She likes to give out tests as shown in The End. She also seems to like pretty dresses, though it may just be the dress' powerful effect of beauty that causes her to like it. She is Gumball and Darwin's arch-enemy.
In The Ape, she is shown to have many awards, except the "Favorite Teacher Award", because nobody likes her. She pretends to make friends with Gumball and the Watterson family and cozies up with them in order to win the award. It was shown that Nicole bears a hatred for Miss Simian because she kept calling her a "loser" all her life. She is soon convinced that Miss Simian has changed, but later finds out that she was faking her friendship. This ensues in a wild car chase which ends in Miss Simian falling off a bridge. Despite being seriously injured, she gets the award, saying it was worth it.
In The Apology, Every time she turns around the children gasp. In disgust, they do whatever they can to block the ugly sight. Gumball and Darwin decide to write her a note, and make it into a paper airplane to throw at her. Unfortunately, the paper airplane goes straight into Miss Simian's eye. Next, they are in the office, as Miss Simian yells about how bad Gumball and Darwin are to Principal Brown. Principal Brown asks why the boys threw the paper airplane at her, so they tell him to read the message. Miss Simian goes to close the window, right when Principal Brown finally notices that her butt is exposed. He informs her of the situation, and she's very embarrassed and furious. However, the boys aren't punished for their actions, and Principal Brown tells Miss Simian that she should apologize. She goes berserk and wrecks his office.
Miss Simian is determined not to apologize, and she conspires to prove that Gumball and Darwin are bad kids. First, Gumball gives her his report card, and Miss Simian takes them to Principal Brown's office on suspicion of forged signature. Richard is called in to sign the suspension card, and to their surprise, his signature exactly matches the one on the report card.
Next, Miss Simian plants a $100 bill at the library for the boys to find, therby trying to prove they are thieves. Of course, Gumball and Darwin are overjoyed upon the discovery of money. However they both agree that the $100 bill is corrupting them, so they throw it away.
Later, Gumball and Darwin are having their lunch when they start discussing about a rumored upcoming fight, and who's going to be in said fight. It turns out they are the ones involved in the fight. The classmates egg them on, but utlimately Gumball and Darwin resolve peacefully. Miss Simian, the one who staged the fight, is devastated.
After a brief, one-sided conversation with the skeletal remains of her father at the museum, Miss Simian makes one final attempt. She enters the boys' restroom to spray graffiti in order to frame Gumball and Darwin. It backfires on her, as she has got spray paint all over herself. Principal Brown is fed up with her attempts, and warns to stop or else he will fire her. Truth be told, he's sad that it may mean the end of their relationship if Miss Simian is really this kind of person.
Gumball and Darwin see Miss Simian and Principal Brown's plight, and they plan to commit a bad deed and get themselves caught in order to preserve the faculty staff's relationship. They retrieve the spray paint can from the restroom, when they get caught by Miss Simian. She goes into a bout of primal ape rage, and chases them through the hallway. They manage to delay her by unintentionally slamming a locker door into her face. They proceed outside, where Gumball begins spraying paint onto Principal Brown's car and Darwin unsuccessfully throws rocks at his office's window. They get into an arguement about Darwin's poor throwing skills when they are caught by Miss Simian. At last, she realizes she finally can take them to the principal's office, only to be surprised upon learning Gumball's intent. She quickly excuses the boys to clean up the car, and as the boys leave, she whispers an apology to them. As she goes back to cleaning, Principal Brown peeks out of his car, and asks her for an explaination on why his car has been defaced.