Skin
Skins are only unlocked in Rayman M/Arena with half of the characters earning them who are: Globox, Henchman 800, Teensies, Henchman 1000 and Rayman. Each character unlocks up to 3 skins, except Rayman, who only gets one. Each skin (but Rayman's) changes the beat for the character's theme to what it is most suited to. (E.g. Globox has his strawberry skin and is racing in the Extreme League. The beat for the Extreme League racing is fast, and the beat for the Advanced League is light and watery. Globox's skin will change the beat from the Exteme League to the Advanced League.) But if it is in its League, it will change to the Beginner League's beat (thumping in the background). The skins do not have this effect on battles. It unnoticable, but may be true that the skins in their league make the race slightly easier.
Globox
Globobx's Advanced League skin is him having a strawberry colour scheme skin. His Expert League skin is him wearing Rayman's shirt, which doesn't fit him, and Rayman's topaz colour skin. His Extreme League skin leaves on his head and the same colour skin for his body.
Henchman 800
Henchman 800's Advanced League skin is a metalic green, and a small, human like eye, with his other completely pink, which could be possibly a brain. His Expert League is a gold and a red paint job. His Extreme League skin is a wooden plating and hints of green paint.
Henchman 1000
Henchman 1000's Advanced League skin is a fine silver body with a purple hat and legs, and his eyes are bright yellow.