Awesome Moment of Crowning: Sort of. He draws the sword out of the stone, the heavens part, and everone bows to him. We don't see the crowning itself but for the in-universe crowd, this is the part that matters.
Baleful Polymorph: He spends a good third of the movie being transformed into various animals, in order to "teach him about life".
Not Allowed to Grow Up: He had three different voice actors (the directors' sons), one of which was going through puberty at the time. The result is squeaky and inconsistent, as he goes from adorable Kid Hero to slightly angsty teenager back and forth.
Seers: He can see the future, and indeed has seen almost all modern technologies and discoveries that mankind would make long after his time. Archimedes wishes he would be more prudent about mentioning future events, as he runs the risk of making Wart sound like a lunatic if he goes around parroting Merlin's predictions.
"Sounds like someone's sick. How lovely! I do hope it's serious — something dreadful."
Voiced by: Martha Wentworth
Adaptational Heroism: Mad Madame Mim is a genuinely villainous character here who tries to kill Arthur because, as she makes no effort in hiding, she's evil. In the Disney comics that later feature her, she is more of a harmless witch or occasionally even a heroic one.
Affably Evil: Madame Mim is cheerful, amiable, and pretty friendly when Arthur blunders into her house, and while he can tell she's unpleasant, he doesn't even realize she's dangerous until she tells him she has to kill him which she says with about as much fanfare as someone saying it's suddenly started raining.
Big Bad: The Marvelous Mad Madame Mim is a aversion because she has only one scene and is not involved with the other scenes.
Card-Carrying Villain: She sings a whole song about how wonderful it is that she's proud to be mad and evil, and she takes "terrible" as a compliment (and finds it lovely when someone's sick—though she doesn't find it so lovely when she gets sick later...).
Combat Pragmatist: In the words of Archemedies, she only wants rules so she can break them.
The Dreaded: If Archimedes' reaction upon seeing her is of any indication, she doesn't have a particularly good reputation.
Laughably Evil: Madame Mim sings a Villain Song about herself complete with dancing and shapeshifting. Merlin is far more restrained.
Laser-Guided Karma / Irony: Her very first line has her hearing a cough and hoping whoever it was had something dreadful and serious. When we leave her, she's stuck in bed sick with something dreadful, but lucky for her not too serious.
Scaled Up: Her final shapeshift in the Wizard Duel is a purple dragon.
Vain Sorceress: Mim defies this trope. She says she could be beautiful if she wanted to be, and in fact, does change herself into such a form as if it were a parlor trick. Then she admits that such a form is only skin deep and she's happy being ugly.
Jerk with a Heart of Gold: Has shades of this. He's insulting and bad-tempered, but seems to genuinely have affection for Arthur, so much so that he risks his life to save him from the pike when Arthur is transformed into a small fish.
Arthur: That big fish almost swallowed me, and Archimedes... he saved me!
Anti-Villain: He acts antagonistic to Wart but he's closer to "strict father" then "antagonist".
Berserk Button: Try pissing off Ector by coming up with (in his view) extremely far-fetched excuses for ducking out on your kitchen duties, or try to defend Merlin's behavior, and you'll send him flying off the handle so far that you'll be doing dishes for the entire castle.
Parental Favoritism: Ector's partiality to Kay is somewhat justified by the fact that Arthur/Wart is only his foster child. Though, while he could be nicer to Arthur, he's not an example of Abusive Parents either... more just strict and demanding, which seems to be his personality in general.
Butt Monkey: He's involved in a few slapstick, particularly in the kitchen scene, along with Ector.
Dumb Muscle: Kay is not very bright and has rather muscular appearance.
Epic Fail: Kay loses a jousting match to an immobile dummy.
Evil Redhead: Again, not really evil, just a jerky older brother.
Jerkass: Far more so than Ector. Until the very end, he acts arrogant, boorish and obnoxious.
Jerk Jock: The medieval version; a rude knight and jouster instead of a football player.
Jerk with a Heart of Gold: Kay is implied to have at least a few gold flecks. At the end when his father demands he bow to Arthur, Kay does so sullenly at first... then after looking at him, does so sincerely.