Chameleons are a species of lizard on Earth and Mobius, known for their ability to change colours to blend into their environment.
The most regularly seen chameleon in Sonic the Comic is Espio of the Chaotix Crew. Another known one was Loot the Treasure Seeker, who Tails and Harry Mole thwarted at the Museum of Arty Art.
Outside of the Mobian-centric stories, Chameleon was the name given to Casey by The Voice when he battled in Wildside in the Kid Chameleon series. By uttering the word 'chameleon', Casey was able to transform into a number of beasts and warriors, though he had no control over the forms he would take.