In Super Mario Bros.

King Bowser Koopa, known in Japan as Koopa (Japanese: クッパ), a fictional turtle-like character from Nintendo video games, is Mario and Luigi's arch-nemesis (although he has joined forces with them in a few games). He has repeatedly kidnapped Princess Peach and has repeatedly attempted to conquer the Mushroom Kingdom since his first appearance in Super Mario Bros.

Appearances in video games
In all of his various incarnations throughout the Super Mario Bros. series, he has been depicted as obsessed with Princess Peach. He is also consistently depicted as nasty, brutish, and not particularly bright.

In Super Mario Bros. 3, Super Mario World, and Super Mario All-Stars, his seven children helped him in his unsuccessful conquest.

It is arguable whether Mario and Bowser first encountered each other when they were babies in Super Mario World 2, or from old manuals that they actually first encountered each other when Bowser took Princess Peach captive in Super Mario Bros. It is generally held that Baby Mario and adult Mario are the same person, and more recent Nintendo manuals agree with this conclusion.

In Super Mario RPG Bowser teams up with Mario, Peach, and their two new friends Mallow and Geno in order to get his castle back from an extra-dimensional invader named Smithy (or Kajioo in Japan). This is the only other game in the series in which Mario and Bowser have intentionally worked together, aside from Superstar Saga, and the only Mario RPG game in which Bowser is a member of your party.

In Super Mario 64 and Super Mario 64 DS, he steals Peach's castle, and Mario (and his friends) have to collect all the stars to restore the POWer of the castle. In Paper Mario he steals Peach's castle again with the Star Rod.

In Mario and Luigi: Superstar Saga he tries to kidnap Peach but somebody else has gotten there first and so ends up in a complicated adventure to help Mario get her back so he can kidnap her.

In Super Mario Sunshine, it is revealed Bowser has a son named Bowser Jr. Some people believe this is the same "Baby Bowser" who in Yoshi's Story converts Yoshi's Island into a storybook. This has no proof, because Mario doesn't appear in the game. Also, at the end of Super Mario Sunshine, it's revealed that Bowser had told Bowser Jr. that his mother was Princess Peach; a fallacy admitted later on by Bowser. This has led some fans into believing that Bowser somehow has a crush on Princess Peach, hence partially why he is so obsessed with capturing her.

In Paper Mario: The Thousand-Year Door, Bowser is enraged when he discovers that someone other than himself has captured Princess Peach and sets out on a mission of his own to find her, only to be beaten by the punch at every turn.
Bowser also appears in secondary Mario Games like Super Mario Kart, Mario Kart 64, Mario Golf, Mario Tennis, Tetris Attack, Mario Kart Super Circuit, Mario Kart: Double Dash, Mario POWer Tennis and Super Smash Bros. Melee. In these games he is not the villain, but rather a selectable character that the player can choose to play as. A giant Bowser also cameos in the SNES port of the original Sim City when a monster disaster strikes.

Appearances outside of video games

Bowser has been known by different names over the years, which have since amalgamated into his current title. In Japan, he has always been known as simply Koopa. When Super Mario Bros. came out in the US, he was given the more American name of Bowser, King of the Koopas. Confusingly, the American cartoons, such as The Super Mario Bros. Super Show (where he had an amazingly large sense of humor and delivered most of the show's one-liners), and the Super Mario Bros. movie consistently referred to Bowser as "King Koopa", never Bowser (although he was occasionally addressed as Bowser in The Adventures of Super Mario Bros. 3). Somewhere along the line the two names merged, and he is now known in America as being Bowser Koopa, with "Koopa" as his, and his children's, last name.

In addition to Bowser's appearences on the cartoons, he also was briefly mentioned in Gex 3 on the Playstation (though there was no mention of him in the N64 version, amazingly enough).

Confrontations with Bowser

The following is a description of fights with Bowser:

Spoiler warning: Plot and/or ending details follow.

In Super Mario Bros. and Super Mario Bros.: The Lost Levels, Bowser (and those disguised as him) will breathe fire and jump periodically. As Mario or Luigi, you had to run or jump past him and touch the axe at the other side. The player could also defeat him by shooting fireballs at him. In worlds 6 and higher, he also threw hammers like Hammer Brothers. Bowser is mimicked by a Goomba in World 1, a Koopa Troopa in World 2, a Buzzy Beetle in World 3, a Spiny in World 4, a Lakitu in World 5, a Bloober in World 6, and a Hammer Brother in World 7. The real Bowser appears at the end of World 8.
In Super Mario Bros. 3, Bowser again breathes fire, this time from above, being shot downward at a 45 degree angle and then turning and moving horizontally as it approached the ground. Bowser jumped at the player, which crushed bricks that would eventually make him fall into a pit.
In Super Mario World, he rode his Koopa Clown Car (it better resembled a hot air balloon), and threw Mecha-Koopas at the player. He would later drop giant balls, and finally bounce his "car" up and down in a final attempt for victory.
In Tetris Attack, Bowser would appear in Stage Clear mode, representing a very difficult level (a role that would be filled in by Butch & Cassidy and then Giovanni in Pokémon Puzzle League). He was also the final boss on the hard and very hard level story modes.
In Super Mario RPG, Bowser is fought at the very beginning of the game, where he and Mario were on separate chandeliers, and could be temporarily defeated by damaging the chain that held Bowser's chandelier in place.
In Super Mario 64, Bowser, confronted three times over the course of the game, would again breathe fire, but in 3D this time. In the final battle, he would do a big jump to remove sections from the battle platform. Mario could defeat him by grabbing his tail and throwing him at spiked bombs.
In Paper Mario, Bowser would beat Mario at the beginning of the game, but could be defeated at the end, even with the help of a magic spell that would POWer him up to the point of invincibility, if it were not for the combined efforts of Princess Peach, Twink, and the Star Spirits.
In the Mario Party series, Bowser will usually arrive when you land on a Bowser space, presenting the players with Bowser minigames, the Bowser shuffle (players swap places on the board) or even the Bowser Revolution, in which all of the coins would be evenly distributed amongst the players.
In Mario Party 5, Bowser appears at the end of Story Mode. The player must first force him to stomp the same area until he falls through (in a confrontation similar to Super Mario Bros. 3, only done in an overhead view). Then he'll take a potion and grow, and shoot some fireballs at you. Sometimes a rock will appear, which the player can throw at Bowser to damage him.
In Luigi's Mansion, Luigi must defeat Bowser as the final boss using his Poltergust 3000 to complete the game. This, however, is not technically a Bowser incarnation, but a Bowser robot piloted by King Boo.
In Super Mario Sunshine, Bowser is laying back in a hot tub, and again breathed fire at Mario, while Bowser Jr. shot homing missiles. The only way to win is to destroy the hot tub by hitting 5 specific points coming out the edge of it.
In Mario and Luigi: Superstar Saga, Mario must defeat Bowser near the beginning of the game, though the two join forces in an attempt to recover the stolen voice of Princess Peach. He is later fought while accompanying Popple in the guise of Rookie. Finally, he is possessed by the spirit of Cackletta, and Mario and Luigi must defeat him one more time as Bowletta.
In Paper Mario: The Thousand Year Door, Bowser fights Mario once in a wrestling match and later just before the final boss, in which he is accompanied by Kammy Koopa. In both confrontations, he can be defeated with the same RPG tactics that are used for all battles in the game.

Bowser the wardrobe artist

In The Super Mario Bros. Super Show, Bowser/Koopa had a particularly large wardrobe, and every so often (mostly in movie parody), he'd put on one of his many costumes and/or take on a new alias. Among his many alter-egos:

Kid Koopa (cowboy)
Kaptain Koopa (steamboat captain)
Emperor Augustus Septemberus Octoberus Koopa (Roman emperor)
Moonman Koopa (cosmonaut)
Koopa Khan (parody of Genghis Khan)
King-of-the-Road Koopa (biker)
Count Koopula (vampire)
Blackbeard Koopa (pirate captain)
King Googoo Gaga Koopa (baby)
Professor Kooparity (parody of Professor Moriarty)
The Pied Koopa (parody of The Pied Piper)
Dr. Koopenstein (parody of Frankenstein)
Koopfinger (parody of James Bond villain Goldfinger)
The Sheriff of Koopingham (parody of the Sheriff of Nottingham)
Koopa Nemo (parody of Captain Nemo)
Koop-zilla (parody of Godzilla)
Koopa Klaus (parody of Santa Claus)
Red Baron Koopa (pilot)
Al Koopone (parody of Al Capone)
Rappin' Koopa (Disc jockey)
El Koopitan (Spaniard)
Koop Tut (Egyptian pharaoh)
Redcoat Koopa (redcoat)
Alley Koop (caveman)
Klaimjump Koopa (cowboy)
Kool Koopa (greaser)
Karate Koopa (samurai)
Billy the Koopa (cowboy)
Judge Koopa (judge)
Warden Koopa (warden)
Barra-Koopa (merman)
Kolonel Von Koop (Nazi)
Kangaroo Koopa (Australian hunter)
Darth Koopa (parody of Darth Vader)
RoboKoopa (cyborg)

Bowser in the Super Smash Brothers series
Bowser appears in the second Smash Brothers game, Super Smash Brothers Melee. He is the heaviest selectable character in the game, making him rather difficult to KO. Additionally, his attacks are exceedingly POWerful. However, his his large size can be a liability, and his attacks are as slow as they are POWerful. He is the last character fought in Adventure mode, and on harder difficulties he may transform into Giga Bowser, an even larger more POWerful version of Bowser.

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A link to the article alone would have been cool, too.

Quite informative.

A link to the article alone would have been cool, too.

Quite informative.

Oh sorry I thought people would rather read it. oh my bad.

No problem, basically.
I just thought it's easier to post only the link.