Chaos

  Chaos  is a Chao mutated by the Chaos Emeralds that acts as a guardian for its species, protects the Master Emerald, and provides clear water around the altar of the Master Emerald.It is a water-like being that can easily manipulate its body, allowing it to stretch limbs or liquefy itself. Without any Chaos Emeralds, it is known as Chaos Zero, but with each Emerald it absorbs, it transforms into a more powerful form, eventually becoming "Perfect Chaos" with all 7 Emeralds.

After the Echidna tribe attempts to steal the Chaos Emeralds, harming various Chao in the process, Chaos absorbs the negative energy of the Emeralds, becomes Perfect Chaos and causes chaos until being sealed inside the Master Emerald with Tikal. From this it forever earns the title of 'God Of Destruction.' It is released thousands of years later in Sonic Adventure, so Dr. Eggman can use it to conquer the world. Chaos, still filled with negative energy, absorbs Chaos Emeralds given to it by Eggman. After being defeated by Knuckles, he returns to Angel Island with the 6 Chaos Emeralds he took away from Chaos. Chaos tracks down the 6 emeralds at Angel Island then discovers the final Chaos Emerald in the Tornado 2 and he absorbs the last emerald and becomes Perfect Chaos. He then floods Station Square but is then defeated by Sonic who has absorbed the positive power of the Chaos Emeralds, which purifies Chaos, and allows it to leave peacefully with the spirit of Tikal. It reappears in Sonic Adventure 2 as a bonus character and in Sonic Battle as a playable character. He reappears in his perfect form in Sonic Generations as a boss. He has a new look different than how he appeared in the Dreamcast game, with green teeth and dark blue reptilian skin for the upper half of his body. The lower half of his body is still made up of water. This was supposed to be how he always looked, but the technology of the Dreamcast at the time made this look impossible.

Froggy

Froggy is a frog, and the best friend and buddy of Big the Cat. He has been rescued by Big and friends when he has gone missing.

BIG THE CAT

                                                                

Big the Cat is a large, purple anthropomorphic cat with yellow eyes and long ears who first debuted in Sonic Adventure on the Dreamcast. Big is laid-back and easygoing, which is reflected in his speech. Strong but gentle and a little slow, he lives a normally peaceful life in the jungle with his best friend "Froggy." He loves fishing, and he is never without his favorite rod and lure.

He first appeared in Sonic Adventure, where he is after his best friend, Froggy, who swallows a Chaos Emerald and grows Chaos' tail. Big was also playable in Sonic Shuffle. Next, he appeared in Sonic Heroes helping Team Rose save Froggy and Chocola  (Cheese's twin brother) who had been kidnapped by Metal Sonic. He also appeared in Sonic Chronicles: The Dark Brotherhood as one of the main characters. Big also had a minor role in the DS version of Sonic Colors.
He was a playable racer in Sonic & Sega All-Stars Racing, and made cameos in the Mario & Sonic series of games.
Big was featured in a McDonald's promotion between December 3 and December 27, 2004. One of eight handheld dedicated consoles packaged with Happy Meals featured Big recreationally fishing.
In a preview of Sonic and the Secret Rings, Nintendo Power praised the exclusion of Big from the game, referring to him as a "dim-witted, morbidly obese feline". However, Big later made his way into the game.