Espio the Chameleon

From Wii Wiki

Espio the Chameleon is a purple chameleon who is an expert ninja. He appears in Sonic Heroes. He is described as the "guardian of honor" of the Chaotix. He is not concerned by danger, and often yearns to face it in order to use his ninja skills. With his extensive training in ninjutsu and an ability to turn himself invisible, he is able to move around unnoticed. However, a blunder like a sneeze could cause him to become visible again.