Miss Lucy Simian is the main, later secondary antagonist turned anti-villain of the animated series The Amazing World of Gumball. She is Gumball's sadistic teacher, who has been teaching second grade for 300 millenia. She utterly despises Gumball and does whatever she can to foil his plans. Principal Brown is hopelessly in love with her, and she returns the feeling, as shown in The Mystery, where she says "My poor, sweet Nigel!", and in The Party where they're seen crashing a party and kissing in the end of the episode. She was also portrayed as the main antagonist in The Mystery.
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 former Archenemy after Rob took the role as the main villain.
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, after finding out that her skirt was up, she blamed the boys for thinking it was funny and went out of her way to prove they were bad.
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.
In The Joy, Miss Simian stop the students from smiling and made them depressed and sad.
In The Lie, she attempts to stop Gumball's made-up holiday called Sluzzle Tag, but in the end, redeems herself when Darwin gave her a Sluzzle Tag gift.
In The Countdown, she threatens to expel Gumball and Darwin from school if they're late, and while Gumball and Darwin race to school with an on-screen timer, they find Miss Simian in her car and chases them, eager to expel them, but fortunately Gumball (who broke the fourth wall) crashed onto the screen, stopping the on-screen timer and froze time.