Dr. Kroopa is a famos scientist who once worked for Bowser uring the time of Mario and Luigi Superstar saga. He stayed in the koopa cruiser ever since it crashed into stardust fields.
In the second storyline, Koopa tournement 3.0, Koopina is a cyborg, and his arm and left eye can be seen on Dr. Kroopa's Lab Screens. Dr. Kroopa was the cretor of koopina's Arms and left eye, but he hadn't know they would be used for evil.
Eventually Dr. Kroopa Is hypnotised and fights Mario and Luigi, but this may not happen until somewhere around chapter 13.
Dr. Kroopa Graduated from the same colledge of Proffesor E.Gadd, and they are very good friends.