Unlock The Ooze and Comix Zone games
Have a Sonic Heroes completed game save file on your Xbox hard drive. When you start the Sonic Mega Collection Plus game up, you will have Comix Zone and The Ooze unlocked from the start!
Unlock Blue Sphere game
Play Sonic the Hedgehog and Sonic 3D Blast 20 times each, exit to the title screen and then go back into the game select screen and Blue Sphere will now be unlocked.
Unlock Flicky
Play Mean Bean Machine at least 30 times to unlock Flicky. You can just enter the game and exit as soon as it loads up. After the 30th time, exit to the title screen and enter the games menu again.
Unlock Knuckles in Sonic 2
Play Sonic the Hedgehog 2 and Sonic Spinball 20 times each.
Debug Mode
To enter Debug Mode, play these sounds from the level select screen: 1, 9, 9, 2, 1, 1, 2, 4. Press Start and hold A. To start debugging, press B, then you can select any sprite in that level and put it on the screen. To select a different sprite, press A, and to place it on the screen, press C. Note that sprite selection is different from Zone to Zone. Also, instead of displaying the time elapsed, it displays the number of sprites currently on the screen.