Using the JTAG/RGH's ability to swap memory, you can install DLC that replaces Classic Sonic with Mighty the Armadillo, or Modern Sonic with Shadow the Hedgehog (complete with Chaos Blast SFX).
You're referring to a popular topic among Xbox enthusiasts! Generations Sonic -Jtag RGH DLC-
Why is this important for Sonic Generations ? Because Sega produced three distinct waves of DLC, two of which were locked to PC or Japan-only arcades. JTAG/RGH bridges that gap. Using the JTAG/RGH's ability to swap memory, you
Here's a post covering Generations Sonic, JTAG, RGH, and DLC: and DLC: : After copying
: After copying, open a management tool like XM360 . Use the "Rescan All" function to detect the new DLC. If the content shows a "closed lock" icon, select Unlock DLC to make it playable in-game.