Sonic the Hedgehog 2 has been fairly vague with its story details so far, but the reveal that fan-favorite character Knuckles the Echidna will be playing a major role means that the film could be setting up another popular group from the series: the Chao. The Sonic games are surprisingly packed with lore, meaning that carrying over only a few of the games' elements to the movies could have major implications. The trailer hints that Dr. Robotnik's plan this time around will greatly expand the world of Sonic the Hedgehog, adding more characters and possibly an even greater villain.
Sonic the Hedgehog (both the movie and the games) follows the blue blur as he attempts to save his friends and his world from the villainous Dr. Robotnik, who is given the demeaning nickname Dr. Eggman by Sonic. The trailer for the much-anticipated sequel Sonic the Hedgehog 2 hasn't explained much, but it has shown that Dr. Robotnik has somehow obtained the power of the Master Emerald as well as the companionship of Knuckles the Echidna, a red powerhouse whose ego is the only thing bigger than his fists. In the games, Knuckles is a member of the Echidna tribe who is tasked with guarding the Master Emerald, a mystical gem that grants its wielder immense power. Although the movie's setup seems to be fairly simple, it is entirely possible that a wealth of interweaving elements from the games could find their way into Sonic the Hedgehog 2.
The savage Echidna Tribe appeared in the first Sonic film, attacking Sonic and Longclaw the Owl near the beginning of the film. Although they were barely featured, the introduction of Knuckles and the Master Emerald means that the sequel will probably greatly expand on the tribe's lore. In the games, the Echidna Tribe takes control of the Master Emerald from the Chao, a race of blue pet-like creatures that are beloved by fans of the Sonic Adventure series of games. Because of the Chao's importance to the Master Emerald storyline and the effect they could have on the entire film series, it is incredibly likely that they will appear in some form in Sonic the Hedgehog 2.
While the Chao's role in the film will have to be slightly tweaked, the writers could easily fit them into the film while still keeping the core of their story. Since Dr. Robotnik and Knuckles seem to have teamed up, it is entirely possible that, while attempting to get back to Earth, Robotnik saw the opportunity to manipulate the Echidna Tribe into stealing the Master Emerald for him. Not only would their introduction make story sense and appease fans of the series, but the Chao are also incredibly marketable, as their entire point in the games is for players to train, customize, and play with their various Chao. On top of all these reasons though, the introduction of the Chao also necessitates the introduction of one of the series' major villains - Chaos, the immortal guardian god of the Chao.
Alongside Robotnik and Metal Sonic, Chaos is one of the villains in the Adventures series, a being who is infuriated when the Echidna Tribe slaughters the Chao and unleashes himself upon civilization. Arguably the most powerful villain in the series, the introduction of Chaos would be a perfect way to ramp up the stakes for the sequel, providing a spectacle and a sense of danger that was lacking from the original film. Several times throughout the trailer for Sonic 2, a large spiraling cloud shooting out green lightning is seen. This cloud could contain some form of Chaos, with the being either coming to seek revenge on Knuckles and Robotnik, or being used by Robotnik to wreak havoc on the world. With all of the clues laid out in the trailer, the introduction of Knuckles could be the perfect opportunity to introduce Chaos and the Chao in Sonic the Hedgehog 2.
