Kamek

Kamek is a Magikoopa that took care of Baby Bowser during the events of Super Mario World 2: Yoshi's Island, Mario and Luigi: Partners in Time, and Yoshi's Island DS. He apparently has a high rank in the Koopa Kingdom army (or Koopa Troop), since during this time he both raised Bowser and took control of his army until he was old enough. Kamek also knocked Mario into space in Super Mario Galaxy. Kamek is a boss of the Yoshi's Island series and Mario Party DS. He and Kammy Koopa, another underling of Bowser, serving him in the Paper Mario series, are often confused with each other. He's also part of the Mario Kart Wii bike Magikruiser. In New Super Mario Bros. Wii, it is unknown if Kamek died when Bowser knocked him into the lava.

New Super Mario Bros. Wii
Kamek is a recurring villain in the game, appearing mostly during boss battles against the Koopalings. He uses his magic to add an effect in the arena, and thus make the battlefield more difficult than the Mini-Boss encounters with the Koopalings, such as enlarging a Chain Chomp, moving platforms, etc. He appears as the first Mini-Boss of the 8th World, where he battles in a way similar to Yoshi Island. After his defeat he's seen during the game's final boss battle in which he appears as a disguised Princess Peach and uses his magic on his king. He pauses for a moment to check if his spell worked, and suddenly Bowser appears in gigantic size, knocking Kamek into lava, it is unknown if Kamek died at this point (however given that Bowser has cheated death in previous games, this seems unlikely).

Super Mario World 2: Yoshi's Island
Kamek is the primary antagonist in this game kidnapping baby Luigi. Also during the events of the game, Kamek uses his magic on the bosses. At one point, he shrinks Yoshi with his magic.

Mario and Lugi: Partners in Time
A younger version of Kamek appears to (apparently) obey Baby Bowser's every whim, usually getting him cookies and the like. After Baby Mario foiled his plan of kidnapping Baby Princess Peach and while the Shroobs attacked the castle, Baby Bowser called on Kamek to bring over the Koopa Cruiser to get him (plus Baby Peach, Baby Mario and Baby Luigi) out of the castle.

Mario and Luigi: Bowser's Inside story
Kamek makes a brief appearance after bowser gets launched out of Peach's Castle. He teaches Bowser how to punch and breathe fire. Also, at the end of the game, after the credits, he tends Bowser after his latest beating by the Mario Bros.

Mario Party series
Kamek was introduced to the Mario Party series in Mario Party 5. Since then, he has appeared in most Mario Party games as an orb or capsule. In later Mario Party games, his role was increased to hosting events on the board maps.

Mario Party 5-7
Kamek was introduced as a capsule in Mario Party 5. When a character uses a Kamek capsule or lands on the space, Kamek will appear and shuffle all the players capsules, dividing them evenly among each of the players. The player that summons Kamek will always get a capsule, despite the number of capsules each character is carrying. Kamek appears as an orb in Mario Party 6. In this game, Kamek will change an opponents character space into the space of the person that used his orb. Thus, giving the summoner the opponent's orb space. Kamek reprises his role as an orb in Mario Party 6. In this game, Kamek's role as an orb is different. When a player lands on an opponent lands on a character space containing a Kamek orb, Kamek will appear and steal all the opponents orb, giving them to the space owner,

Mario Party 8
Kamek's role in the Mario Party series increased to the board maps in this game. In Shy Guy's Perplexed Express, Kamek will randomly shuffle the trains when a character lands on a certain happening space. This may cause some characters to lose their ground on gaining a star. Kamek also appears in Bowser Warped Orbit, where he will switch a players candy with an opponent, similar to his role as a capsule in Mario Party 5. Kamek also appears as one of the computer controlled racers in Moped Mayhem.

Mario Party DS
Kamek gained a much more significant role in Mario's DS adventure, where he received his own board, Kamek's Library. There he would cast spells to cause trouble for Mario's gang. He later appeared as a boss, where he would throw magical bursts at the player as they attacked him with Ink blobs, in the Minigame Book Bash.

Mario Party 9
This is Kameks most significant role due to the fact that he has become a playable character after beating the story mode once. In story mode he plays for Bowser so if he wins he will return the mini stars collected to Bowser resulting in the player going through the party board again 

Powers & Abilities
As Bowser's right hand man and leader of the Magikoopas (possibly alongside Kammy Koopa) Kamek has immense (and perhaps unparalleled) magical powers, which he has demonstrated in several games. He can use his magic for a multitude of different effects, such as the usual magic bolt used by the Magikoopas, being capable of turning rubble into living enemies, damage his foes, etc. Amongst his most powerful feats of magic are the ability to change the landscape to make battles much more difficult for Mario and Co. and even alter the size of living beings, mostly enlarging foes to gigantic size, Bowser being perhaps most astonishing example to date, growing to such size that even lava was harmless, even though in previous games it defeated him. He can also use this ability to shrink his foes, but he mostly uses the former. He is capable of flight through his broom, and is capable of teleportation. The fact that during New Super Mario Bros: Wii. he used his magic to aid the Koopalings, strongly implies he's much more powerful than them in magic, likewise he has no physical prowess whatsoever. His magic is powerful enough that during Mario Galaxy one blast of magic, was sufficent to literally catapult Mario into space.