When both games are owned on the same console, an exclusive "Episode Metal" is unlocked.
Despite the game continuing after the fairly plot-heavy Sonic & Knuckles, this title sees things return to Doctor Eggman capturing animals and trapping them in Badnik shells. In the first episode, Sonic must traverse five Zones and defeat his nemesis to save the day.
Episode II sees the return of the Little Planet, something he anticipated since the beginning of the first episode. He returns there and finds that Metal Sonic has survived his last encounter with Sonic, so increases Metal's power. Sonic and Tails pursue Eggman throughout his new Zones, leading to his new Death Egg which has been built around Little Planet. The destruction of the ship with the planet still inside is avoided by the heroes returning to Planet Earth in escape pods.
- Splash Hill Zone (similar to Emerald Hill Zone)
- Casino Street Zone (similar to Casino Night Zone)
- Lost Labyrinth Zone (similar to Labyrinth Zone)
- Mad Gear Zone (similar to Metropolis Zone)
- E.G.G. Station Zone (similar to Death Egg Zone)
Additionally, Sonic can enter the Special Stage to collect the 7 Chaos Emeralds. The environment is very similar to Sonic 1's , but this time involves the player manipulating the stage itself, rather than Sonic.
Episode II sees even more new Zones, although there are more original level designs:
- Sylvania Castle Zone
- White Park Zone
- Oil Desert Zone (a combination of Oil Ocean Zone and Sandopolis Zone
- Sky Fortress Zone (similar to Sky Chase Zone, Wing Fortress and Flying Battery Zones)
- Death Egg Mk.II Zone
This episode's Special Stages are structurally similar to Sonic the Hedgehog 2's.
During the run-up to the game, Sega released concept art of Badniks that would be featured in this game. The entries were actually all classic Badniks that would be getting a chance to return. As well as these, a competition was also run that involved fans sending in their own updated concept art of classic Badniks.
Badniks that made it to the first episode and are somewhat involved in STC are:
The second episode reveals some new Badnik designs, although there are more returns:
Sonic the Comic adaptation
To date, there has not been an adaptation of the first episode into Sonic the Comic Online and, except a possible flashback (since the game occurs in the past) or appearances of the game's Zones and Badniks, it isn't likely that there will be one. However, like how Archie has done, the writers may simply deem the game canonical to STC, rather than adapt.
Four of Episode II's new Badniks appeared together in Issue 261's "To the Hero of Mobius". Robotnik ordered the new creations to conquer the Metropolis Zone, but were stopped by a combination of Tails and Amy Rose.
In Issue 253, Iain Stewart played the game for the Review Zone and awarded it 79%. 'Raves' were that half of the Zones were "absolutely brilliant", the graphics had flair and there was promise for the next episodes, but lamented that it felt like it was just an upgrade of the original Sonic game.
Seumidh MacDonald also provided a review for the title, this time for the iOS edition. MacDonald didn't give the version a score, but said it was inferior to the console installments and mobile owners should stick to re-released editions of Sonic 1 and 2.
The game before Episode I was Sonic & Sega All-Stars Racing. The next game after the completed series is Sonic Jump. Between the two episodes came Sonic Free Riders, Sonic Colours, Sonic Generations and Mario & Sonic at the London Olympic Games.