Sonic the Hedgehog CD (Mega-CD prototype; 1992-12-04)/Hidden content

Back to: Sonic the Hedgehog CD (Mega-CD prototype; 1992-12-04).

2nd Sonic

By pressing on the second Control Pad, a second Sonic (rapidly flickering to simulate semi-transparency) will spawn behind the first one, which can be controlled by the second player. This second Sonic controls identically to the first and can interact with the environment in exactly the same way, however the camera does not follow him. Stray too far from the viewport and the second Sonic will warp back to the position of the first.

Any items collected by the second Sonic will be applied to the first.

Unused content

Art

Art	Description
	Tons of animations for Sonic exist on the disc, but are left unused as only two Zones are playable. Many would be used in the final game, however some are left unused there too.
	A black-and-white death sprite for Sonic. It was unused in Sonic 1, so it's likely a leftover.
	Sprites for a log bridge. The code for the bridge object is unreferenced, but its graphics still get loaded into VRAM, and its mappings are also referenced in the debug mode object list.

Objects

Art	Description
	Object ID 04. It moves downwards quickly for a bit and then disappears, overwriting the level blocks with a singular block as it moves down. This object survives all the way into the final game, where unused graphics suggest it was meant to be a waterfall object. Video showcasing the object.
	Object ID 08. Interacting with this object causes the level layout above it to shift down by 8 blocks, as if it is collapsing. It was removed by the 510 prototype. Video showcasing the object.
	Object ID 25. In the object list, this ID just points to a blank object. However, there is leftover code for a bridge object that was assigned to this ID (R11A__.MMD has it at location 0xBCA4). By re-adding the pointer back to the object list, it can seen that bridges were actually already placed in the stage. If debug mode is also re-enabled via hacking, bridges can be placed with it. Video showcasing the object.
	Object ID 27. An unfinished tilting platform whose graphics are loaded at certain points, particularly the log bridges. It was removed by the 510 prototype. Video showcasing the object.
	Object ID 29. Likely a preliminary swinging platform intended for Tidal Tempest. Spawning this object with a subtype of 00 will cause it to underflow and spawn a 255-chain platform, leading to immense load times and lag. Video showcasing the object.

Stage select

A stage select exists in the 0.02 prototype, but it cannot be acccessed by normal means. By changing byte 0xA1A in track 1 to "01 1A", it can be accessed in an emulator, although all options but 1-1-A lead to the Time Attack screen.

Salad Plain Good Future

By changing byte 0xA1A in track 1 to "00 70" or "00 58" it is possible to access the Good Future versions of Salad Plain Zone 1 and 2, respectively. Despite the Good Future theme existing on the disc (and being used for the "Comin' Soon" screen), the Past version of the music is played.

There is no legitimate way to create a Good Future during normal gameplay, as neither Special Stages nor Robot transporters have been implemented yet.

Slightly different Sonic animations

Some frames of animation are also very slightly different, though in most cases just a handful of pixels separate them from the final game (and are far from obvious).