Adorkable: Not entirely the stereotypical dork, but she has a large brain capacity, which she fills with very advanced subjects such as physics and calculus, she finds homework and extra credit assignments fun, is the youngest person ever inducted into Mensa and has long blonde hair, and a Stalker with a Crush although it's just Angus.
Ditzy Genius: While very book smart due to having super memory, she has very childish moments, such as believing Cameron's ghost story, having way more fun while the rest of the ANTs are playing musical chairs, and her overall naivete. At least somewhat justified in that the character is only 12 at the beginning of the series. Maturity comes with experience.
Dumb Blonde: Subverted since she has the greatest mental capacity on the show, she rarely puts it to good use, as a result, she sometimes ends up looking dumb and childish at times. She begins to play with this trope in "intelligANT".
Token Evil Teammate: She's been developing into one in season 3, even to the point of being worse than Lexi.
Took a Level in Jerkass: From Season 2 onward Olive becomes bossier, more self-centred, and enjoys other people's pain (and doesn't hesitate to inflict pain on others either). In Season 3, it came to a point in one episode where she ended up being worse than Lexi.
He could easily be the snarkiest character on the show but his ditziness keeps him in check.
The Dog Bites Back: Despite his status as the Butt Monkey, Fletcher proves in "feature presANTation" that he does have limits to how much he will endure. In the episode, Fletcher hasn't been able to sleep for days because Angus keeps having nightmares waking him up. He spends the episode helping him with this problem, while Angus acts like a total jerkass towards him. After his final plan to help him ends with them simulating being on a boat, causing Fletcher to still be awake and even fall in a bowl of fish, he finally snaps and, in a particularly impressive and gratifying moment, he not only stands up to Angus, but actually chases him around the school, leaving Angus able to do nothing but run and scream in terror.
Expy: Of Freddie Benson, complete with being the Butt Monkey (but more worse than Freddie's). Though their personalities differ, as well as liking a specific subject (Freddie's Tech knowledge to Fletcher's Art).
Flanderization: His Butt Monkey status is so exaggerated by Season 3 that you're more likely to see him getting hurt and insulted than actually, well, making art.
Genius Ditz: Fletcher's great at art, but thinks snow angels are dead snowmen.
Horrible Judge of Character: At times, he ended up going along with the plans of villains, even when they admit their villainy. For example, he blindly agrees to paint Principal Skidmore even though she admitted to his face that she just uses the A.N.T. Farm as a sweatshop. Another example is when Lexi has Fletcher be the fall guy, so that she wouldn't get in trouble.
Little Boy Seeks Big Girl: Fletcher occasionally tends to forget about Chyna when he's around Paisley, especially whenever Paisley hugs Fletcher. One such example (from the pilot no less) happens to be the pictured example on said Tropes page. So far it happened twice in the show, but he implied about Paisley on "chANTs of a lifetime" when he said he's moving to his 2nd best choice (since Chyna is gone).
Does this again with Kennedy, and has a relationship with her, but it turned out to be a facade.
Nice Job Fixing It, Villain: In the Season 3 Premiere, she made the school run down, hoping a billionaire inventor would fund the school for her own needs, but instead, he decided to make his own ANT boarding school and takes the ANTs under his wing, thus freeing the ANTs from Skidmore's tyranny.