Chaos

Chaos is a water-like creature that appears in the Sonic the Hedgehog franchise. It is known for its ability to change form every time it gets a Chaos Emerald, eventually turning into Perfect Chaos when it has all seven.

Super Smash Bros. Brawl
In Super Smash Bros. Brawl, Chaos makes a cameo as a sticker.

Super Smash Bros. Ultimate
Chaos appears in Super Smash Bros. Ultimate as a primary, Advanced-level spirit.

Mario & Sonic at the Olympic Winter Games
Chaos makes two minor appearances in the Wii version of Mario & Sonic at the Olympic Winter Games. One is as a frozen version of its Perfect Chaos form, where it appears for the third segment of the Sonic World routine in Dream Figure Skating, and is defeated by the characters using the Chaos Emeralds. It also appears as a VIP member that gives the player 100 Star Points when spotted.