"Leave her alone! I won't let you take Mama Peach again!" - Bowser Koopa Jr. to Mario, Super Mario Sunshine
Sometimes enlisting your seven evil children to help conquer the world just doesn't work. Ask
Bowser, the
King of the Koopas in
Nintendo's
Super Mario Brothers video games, about that sometime. Sometime in the late 1980s
Bowser and a still-unidentified Koopa female spawned seven children known as the
Koopalings whom he used to help him conquer the
Mushroom Kingdom on several occassions. Each time
Mario and
Luigi defeated the kids and eventually
Bowser himself, and it would seem that the twisted turtle sent his children away for their failure. In the early twenty-first century
Bowser attempted using offspring as part of his demented plans once again, sending his new youngest son, Bowser Koopa Jr., into battle. The littlest Koopa went to scenic
Isle Delfino and, armed with
Professor E. Gadd's
magic paintbrush, he disguised himself as a shadowy
Mario-type figure and vandalized the island from top to bottom, covering it in goop and sending a small army of
Koopas to invade the land. When
Mario and
Princess Peach arrived on the island for a vacation, the local
Pianta people recognized
Mario (or thought they did, anyways) and locked him up for his crimes against the island. His sentence was to clean the island from top to bottom, and it was while washing the island's goop away with the
FLUDD waterpack that he uncovered Bowser Jr.'s plan: a fair bit of revenge against the
famous plumber for kidnapping his mother,
Princess Peach!
Prior to arriving at Isle Delfino Bowser had falsely explained to his son that Princess Peach of the Mushroom Kingdom was his mother and that Mario had kidnapped her. Acting out of anger and honor Bowser Jr. polluted the island strictly to get Mario out of the picture so he could "rescue" the woman he believed to be his mother. Instead Mario defeated his troops, him, and eventually his father, saving the princess once again and expelling the Koopas back out to sea. After a humiliating defeat at Isle Delfino Bowser Jr. has joined his father on the Mushroom Kingdom sports circuit under the Team Koopa banner. So far he's competed in golf, tennis, kart racing, and several organized parties. The little Koopa combines some of the worst traits imaginable - Koopa ambition and childhood immaturity - making him one of the brattiest kids around. He doesn't play well with others, he is extremely selfish, and has been known to thrown tantrums when disappointed... and his father couldn't be more proud.
From a design point-of-view it's unclear why Nintendo created an eighth Koopa Kid when they already have seven other to work with. The original seven children were never very well-defined, so any one of them could have been used in Super Mario Sunshine without causing a storyline conflict. Perhaps the company feared that the kids had been out of the spotlight for so long that audiences wouldn't remember them, or maybe Super Mario Sunshine's design team wanted a fresh start with a new character. No matter what the reason, it would seem that Bowser Jr. is here to stay; in his first two years of existance he's already appeared in more original video games than his seven predecessors did in their entire gaming careers. Note that Bowser Jr. is not the same character as "Baby Bowser" from Yoshi's Story and the early titles in the Mario Party series, but he is the same character as "Koopa Kid" when his name is not consistently translated from Japanese to English.
Bowser Jr. Game Appearances
References:
http://gc.advancedmn.com
http://www.gamefaqs.com
http://www.mariomonsters.com
http://www.classicgaming.com/tmk/
Did I miss an appearance? Let me know.