Bowser is the biggest Opponent from Mario. He got his own Kingdom and his aim is to conquer the Toad-kingdom. So he kidnaps the Princess Peach, who has to be rescued by Mario. In some Games you can control him. He can breathe fire and most of the time, he’s hostile.
Bowser Jr. Is the son of Bowser. His appearance is based on Bowser and his behavior is childish. He is very malicious, and his overeagerness have to be contolled by his dad.
Bone-Bowser is Bowser, who was burned by the lava in his kingdom, but who is still alive. He has got the same Character as Bowser, but he Breathes blue fire.
Drybone is a subject of Bowser. In a duel, he throws bones on Mario, but there are also some Drybones, who walk through Mario’s levels, like the Koopas. In some Games, you can control him.
The Piranha-Plant already exists since the first Super Mario Bros. Regularly; it got a red head with white dots and a green body. There are many different piranha-plants, you can find them in tubes, some of them breathe fire and some of them stretch their neck.
Buu Huu is a Ghost, who comes towards to you, if you look away. But if you hold the eye contact, he won’t come closer.
Bully tries to push Mario from the platform, if he look at him. Big Bully is the biggest one of them, and he’s also their commander.
Kamek is a assistant of Bowser and a wizard. He’s the commandant of the Magikoopas. His character is cruel and terrible, and furthermore he’s able to insert the Circle-square-triangle-trick, which spin the shapes on his opponents.