Bowser

Bowser, also known as the Koopa King, is the main antagonist of the Mario series. Most of his plans involve kidnapping Peach so he can take over the Mushroom Kingdom, but is usually thwarted by Mario.

Appearance
Bowser appears as a massive Koopa with a spiky shell. He wears four spiked bracelets, two on each arm, and has a mane of red hair.

Trivia

 * Bowser sometimes ends up assisting Mario in thwarting an even more sinister villain's plans, as seen in Super Paper Mario
 * Although Mario is his primary nemesis, his plans have been foiled by others. Two of them involved him kidnapping Mario instead of Peach (Mario is Missing, where Luigi stops him, and Super Princess Peach, where his usual kidnapping target Peach herself is the one to stop him).
 * Across five Paper Mario games, Bowser is the main antagonist only three times (in Thousand-Year Door he's an occasional inconvenience while in Super Paper Mario he joins Mario on a quest to stop a much more sinister Count Bleck)
 * Bowser was initially assumed to have eight kids, but recent information from Nintendo has clarified that Bowser Jr is his only one.
 * In Super Mario Sunshine he told Jr that Peach was his mom; Jr figured out the truth sooner than he could tell him but, in true Bowser fashion, declared an intent to beat Mario their next encounter.