King Bowser Koopa, alternatively called Lord Bowser or simply Bowser, is the ruler of the Koopa Kingdom and the leader of the Koopa Troop. His minions refer to him as "Lord Bowser" or some variation of "Your highness" that replaces the word high with a negative trait Bowser has. While the only confirmed biological relative of Bowser's is his son, Bowser Jr., Kamek raised him and continues to serve and advise him. Bowser and the Koopa Troop have tried to take over the Mushroom Kingdom many times. Bowser is known across the world for being the leader of a nation with a formidable military, as well as his monstrous appearance, frequent kidnappings of Princess Peach and his frequent conflicts with his arch nemesis, Mario. He has a group of 7 minions known as the Koopalings who were once considered his children, but are not anymore.
The identity of Bowser's parents, and the exact time of Bowser's birth, are unknown. However, his parents were likely the King and Queen of the Koopa Kingdom at the time, as he was the prince, and he was raised by Kamek.
Super Mario World 2: Yoshi's Island
As a baby, Bowser, who was then Prince of the Koopa Kingdom, encountered the newborn Mario, as well as Yoshi. He attacked Mario in attempt to ride the Yoshi. This was the beginning of Mario's lifelong fight against Bowser.
Mario & Luigi: Partners in Time
Later in Bowser's childhood, he entered Peach's Castle and attempted to kidnap Princess Peach. Toadsworth tried to attack him, but was defeated. Mario then fought and defeated Bowser. Shortly thereafter, Shroob ships attacked the castle. Prince Bowser, along with Peach, Toadsworth, Mario, and Luigi, fled from the castle on the Koopa Cruiser. However, the Cruiser was pursued and attacked by Shroob ships. Bowser, who was in command of the cruiser, successfully destroyed all the pursuing ships. The cruiser flew over Hollijolli Village, attacked Shroobs in the village at the time, and landed in the village.
Super Mario Bros.
Bowser's first fight against Mario as an adult occured when Bowser invaded the Mushroom Kingdom, seemingly for the first time in his adult life. As part of his plan, he magically turned many of the Kingdom's Toads into blocks, and kidnapped Princess Peach, as her magic could reverse the effect. Mario, however, was able to defeat him at his castle, and rescue Princess Peach, thereby stopping his plan.
Super Mario Bros.: The Lost Levels
After this, Bowser once again kidnapped Peach and took her to a parallel dimension. He was once again defeated by Mario.
Super Mario Bros. 3
Bowser once again kidnapped Peach in his attempts to control the Mushroom World, this time taking her an island east of the Mushroom Kingdom contolled by Koopa Kingdom known as the Dark Land. He also sent Airships and his Koopalings to fight Mario, for the first time. However, his armies once again failed to defeat Mario, who reached his castle in the Dark Land. Bowser fought him once again, and was defeated once again.
Super Mario World
Bowser then attempted to kidnap Peach once again, this time while she was in Dinosaur Land. This attempt failed, in the same way his previous attempts did.
The Koopa King then briefly turned his efforts to conquering Jewelry Land. This plan also failed due to the efforts of Mario and Yoshi.
Super Mario Kart
Eventually, Bowser was allowed to participate in a go-kart racing competition that included Mario, Luigi, Princess Peach, and Yoshi.
Super Mario RPG: Legend of the Seven Stars
While the events begin as yet another battle between Mario and Bowser, Bowser's Castle is taken over by the Smithy Gang. Bowser and the Koopa Troop attempt to retake the castle, but fail, leaving Bowser without of any of his resources. Eventually, Bowser teams up with Mario so that he can get his castle back. He also agrees to help restore Star Road. They are eventually successful in doing so.
Bowser's goals are to conquer the Mushroom Kingdom and force Princess Peach to marry him. He is also the nemesis of Mario. He has also tried to conquer areas outside the Mushroom Kingdom, including the Sprixie Kingdom in Super Mario 3D World, and the entire universe in Super Mario Galaxy 1 and 2, meaning that Bowser intends to take over the entire universe. Bowser has also magically transformed Toads into blocks in Super Mario Bros., and forced them to do work for him in Mario & Luigi: Paper Jam.
However, while Bowser insists that he is evil, he is often forced to ally with Mario when a greater threat arises. In Super Mario RPG: Legend of the Seven Stars, Mario & Luigi: Superstar Saga, Super Paper Mario, and Mario & Luigi: Bowser's Inside Story, Bowser was forced to temporarily ally with Mario, though in the latter example he was not aware of this until after defeating Dark Star. However, he has also participated in sporting events within the Mushroom Kingdom. However, this is merely to demonstrate his superiority over Mario through these sports.