Oops yeah you're right I should've said instead "Is not a main Mario character but appears in a main Mario game". Yeah should've said that.
I will agree though the non-Mario characters have no reason to be here but that doesn't necessarily mean their inclusion is bad. I play them all the time!
This character is dangerous but useful. You use him to kill a boss when he pops out of rocks the boss throws at you. You find him in a galaxy trotting game.
This boy and his brother can't seem to catch a break when it comes to being cursed to being Bubble Dragons, they also have the ability to throw Rainbows and have Parasols as weapons.