Sonic & Knuckles/Hidden content

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Hidden area of Hidden Palace Zone

When using edit mode in Hidden Palace Zone, an area above and to the left of Sonic's fight with Knuckles contains a selection of monitors; six on the left, and three on the right.

It has been suggested that these could have been placed here so that clean screenshots could be taken for the Japanese manual. The manual clearly shows Sonic bubble bouncing in Hidden Palace, despite no Water Shields being available through normal playMedia:S&K MD JP manual.pdfMedia:S&K MD JP manual.pdf.

Bow to Knuckles

After Knuckles has let you across in Sky Sanctuary Zone, if you stand in a certain spot and bow (duck), as is customary in Japan, Knuckles turns around and gives a "get going" gesture.

Unused content

Art

	Description
	Vertical hanging sprites for Knuckles.
	A monochrome death sprite for Knuckles.
	An unused, slightly different version of Hey Ho.
	An unused frame for Eggman for use with the Hang Mobile when attacking. It doesn't appear due to a programming oversight.
	An unused piece of the Egg Golem boss.
	A jumping frame for Eggrobo.
	Slot machine image for Super Sonic, intended for the Slot Machine Bonus Stage.
	A flashing S gumball. One could presume it has something to do with Super Sonic.

Objects

Placeable in edit mode

	Description
	A lava stepping stone for the second Act of Lava Reef Zone. Similar objects exist in Act 1, but this unique art for Act 2 is never seen.
	A platform for the Glowing Spheres Bonus Stage.
	"F" gumball, placeable in Glowing Spheres Bonus Stage. When collected it makes the same noise as a Bumper Ball, but it doesn't do anything.

Others

	Description
	A rotating holograph of the Death Egg.
	A solid block that uses art for the slot in the Slot Machine Bonus Stage

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Unused content

Art

Artwork	Name	Description
	Palm Tree	Unseen palm tree graphics. Although these tiles are used in both Sonic 3 and Sonic 3 & Knuckles in the introduction to Angel Island, they are hidden behind leaf sprites. This is how it looks with the sprites layer disabled:
[[Image:|center]]	Death Egg Holograph Projector	Some machine that displays a holograph of the Death Egg. It can be found by hex editing a savestate of Death Egg, act 2. At address A500 replace 01 with E5 and the most northwestern piece will change to this. Thanks to Gold for finding this.

Tails

Tails is playable in the game through hacking. Unfortunately, most of his sprites are missing. A savestate ^(info) (50 kB) of Tails in Sonic & Knuckles is available. If the PAR code FFFF09:02 is used in Sonic & Knuckles, Tails will be usable, but just about every sprite of his, except the transformation sprite, will be missing, basically rendering him invisible (unlike when a savestate is used; a different, glitchy sprite is used in place of Tails's original one). However, his sprites used at the end of Sky Sanctuary Zone to run around the collapsing pillar are actually stored in the Sonic & Knuckles' ROM and therefore are visible. The same sprites are used also in the same context in Lava Reef Zone.

Hidden Area in Hidden Palace Zone

Hidden Palace Zone has a place that is only accessible using debug mode or using Tails in Sonic 3 & Knuckles. Before entering the inside of the Hidden Palace fly from the two steps left until reaching a ledge. Go left to find 6 monitors. If you go right and jump off the ledge you can find 3 more monitors.

8th Emerald

If Sound Test is enabled, and any of the Special Stage options is selected, Sonic or Knuckles is taken to the 1st Special Stage. The end of it however, spawns a Super Emerald. This is when the special stage is marked as clear, but the normal Chaos Emerald amount doesn't rise. The Super Emerald amount will rise, but it has pretty much no effect due to Super Emeralds being unobtainable. This bug WILL allow for the 8th Emerald to be collected once the other six have, though.