"A Chaotic Day" (謎の生命体カオス Nazo no Seimeitai Kaosu?, lit. "The Mysterious Life Form Chaos") is the twenty-eighth episode of the anime series, Sonic X, as well as the second episode of the Chaos Saga. It first aired on 12 October 2003 and 25 September 2004 in Japan and the United States respectively.
- Sonic the Hedgehog
- Miles "Tails" Prower
- Knuckles the Echidna
- Tikal (First appearance; Flashback)
- Pachacamac (First appearance; Flashback)
- Amy Rose
- Lily (First appearance)
- Cream the Rabbit
- Big the Cat
- Christopher Thorndyke
- Chuck Thorndyke
- Chaos (Mentioned)
- Doctor Eggman
- E-12 Behemoth (Flashback)
- ZERO (First appearance)
- "Gotta Go Fast" - Opening theme (USA and CAN)
- "Sonic X" - Opening theme (AUS, NZ and UK)
- "Gotta Go Fast" (shortened) - Closing theme
The episode starts when Sonic, Knuckles, Chris, Big and Chuck are having a coffee break to unwrap the mystery of Chaos. Knuckles says it would be troublesome to defeat Chaos. He explains that after Chaos Control happened, Angel Island was transported into this world, and while Knuckles was guarding the Master Emerald, Chaos destroyed it; which made Angel Island fall into the ocean. Chris asks Big if he saw something in the forest that looked like Chaos while he was looking for Froggy. Big explains that after Froggy swallowed the blue puddle in the previous episode, he grew a tail. Big said he tried to catch him, but he was faster than him and hopped away with something he found in the forest.
Big said it was a purple rock, and Chris figured out it was a Chaos Emerald. Chuck says that they'd better find Froggy fast or it won't survive long, because Eggman will do anything to seize an Emerald and give it to Chaos. Sonic decides to go find Tails to help him look for the Chaos Emeralds, and Knuckles would go look for the pieces of the Master Emerald; while Chris and Big decide to find Froggy together. Sonic goes over to Tails' Workshop at Windy Valley, and explains to Tails about Chaos. Tails says he found a Chaos Emerald which it can be used to find the other emeralds .
Sonic and Tails then hop in the X-Tornado and start searching in Windy Valley. Meanwhile, back at Casinopolis, Knuckles sees that police are investigating the crime that happened because of the hole in the building. Knuckles asks what the crime was, and a policeman says that a glowing object fell from the sky. Knuckles and the police go inside to look. When they find a piece of the Master Emerald, Knuckles picks it up, but is transported to a version of Mystic Ruins 4000 years ago. Knuckles walks around and finds an echidna named Tikal with her father, Pachacamac. Tikal begs her father not to seize the Chaos Emeralds, but as her father ignores her, Knuckles is transported back to Casinopolis of the present. The police decides to let Knuckles keep the piece of the Master Emerald and Knuckles continues his search.
Back in Windy Valley, the X-Tornado has just detected a Chaos Emerald somewhere in the valley. Sonic and Tails walk around and search. Tails is almost blown away by the valley's strong winds, but Sonic catches him at the last second. Tails says that the Chaos Emerald is buried underground, so Sonic uses a Ring to dig underground and successfully finds the Chaos Emerald (Cyan). Eggman arrives and charges at Sonic and Tails and he misses. Tails drops the Emeralds, and Eggman steals them. As Eggman flies away, Sonic jumps on-board his Egg Hornet, but Eggman activates his Egg Hornet Drills and knocks Sonic off. Just as Eggman is about to drill a hole in Sonic's body, Tails throws a Ring in Sonic's hand and spins against a drill. Sonic destroys it and the Egg Hornet. Eggman tries to escape, but the Emeralds he stole fall into a lake.
This is part of his plan, because Chaos is in that lake. Using the two Chaos Emeralds, Chaos 2 transforms into Chaos 4. Chaos 4 uses a windy wave to blow Sonic and Tails away. Sonic attacks, but Chaos 4 submerges underwater and Sonic lands on a lily pad just in time. Chaos uses a tornado to knock Sonic off the lily pad, but there are more lily pads around so Sonic uses them for a surprise attack on Chaos 4. Sonic and Tails think that Chaos has been defeated, but he is not. Chaos 4 uses another windy wave in an attempt to knock Sonic out, but Sonic jumps and tries to attack Chaos 4. When he goes underwater, so does Sonic. Chaos 4 keeps dunking Sonic, but as Sonic feels the wind, and it gives him an idea. He then uses the wind to charge at Chaos 4 at a speed. His plan succeeds as Chaos couldn't reform.
Upset about another losing battle, Eggman retrieves Chaos inside his Egg Mobile and they both go inside the Egg Carrier (from the previous episode). Sonic and Tails use the X-Tornado to follow Eggman, and the chase is on.
As the Egg Carrier floats above Amy Rose and Station Square, the X-Tornado fires at the Egg Carrier. Eggman fires a Cannon at the X-Tornado, but the X-Tornado destroys it. The explosion of the Cannon causes a Flicky to fall out of the Egg Carrier. The Flicky lands on Amy and Amy feels bad for it. Eggman then tells Decoe and Bocoe to fire the Egg Cannon at the X-Tornado and it destroys the X-Tornado's wing. The X-Tornado goes down and Eggman laughs.
Tails and Sonic survive, however. Tails, passed out by the crash, has a dream about being attacked by an E-12 Behemoth, but Sonic pilots the Tornado and destroys the E-12 Behemoth. Then, more E-12 Behemoths come; but Tails pilots the Tornado and he and Sonic destroy them. Tails wakes up and finds bandages around his head, and Chuck tells him that the X-Tornado has taken heavy damage, but they'll get Eggman the next time. Amy and Cream went shopping, so Sonic has gone to check on them. Amy, Cream, Cheese and the Flicky decide to cook a gourmet meal for Sonic after he and Tails crashed. Cream asks the Flicky where it came from and if it has a name. Amy decides to name the Flicky "Lily" and the Flicky likes that name. Lily is happy about her new name, but the happiness didn't last for long. ZERO recognizes Lily, and grabs her and Amy. Sonic hears Amy's scream, and tries to destroy Zero, but no luck. Zero uses his jet packs to fly away and Amy and Lily are captured with the episode ending there.
- In the beginning of the episode, the order of scenes is slightly different between the Japanese and English versions. In the English version, half of Knuckles' flashback begins to play before the opening credits. After the opening, the scene switches to Chris and then to Knuckles before the rest of the flashback plays.
- As with the previous episode, another flashback of Chaos 0 surrounded by the police has been shortened, mostly the scene when the police attempt to shoot Chaos with firearms.
- There is an extra scene in the English dub showing Tails resting with his bandaged head right before a flashback with Sonic
- The following scenes has been cut/edited:
Differences from Sonic Adventure
- Knuckles wasn't present in the fight with Chaos 4 with Sonic and Tails in the episode as he was in Sonic Adventure.
- Amy calls the cyan bird Lily, but in Sonic Adventure, she simply calls it Birdie.
- ZERO kidnaps Amy immediately, but in Sonic Adventure, she escapes from him and then later, she gets kidnapped by him.
- Casinopolis is renamed "Casino" in this episode.
- During Big's flashback to the previous episode when he witnessed Froggy growing a tail, he asks if Froggy had found another Chaos Emerald. However, in the previous episode, he asked what's wrong with Froggy. This is most presumably an error.