Sega's announced Episode Metal Lock-On, an unlockable Sonic 4 story available exclusively to those who own both Episode I and Episode II.
The bizarrely named spin-off game will bridge the story between Sonic CD and the Sonic 4 Saga and reveal the origins of Metal Sonic, says Sega.
Players will speed through four acts, from Stardust Speedway to the events of Sonic 4 Episode II, as Metal Sonic himself. See the first trailer below.
Sonic 4: Episode II, and Episode Metal Lock-On, will be available on May 15 for Xbox Live Arcade (1200 points), PSN ($14.99/ £9.99/€12.99/ AUD$18.25) and PC (£12.99/ $14.99/€12.99/ AUD$19.99).