RedXVI is an old member of the Sonic fangaming community who made the games Sonic MADventure and Thirdscape, as well as almost all of Mystic Realm's soundtrack. His alter ego character from MADventure originally appeared as an easter egg in Demo 4 of SRB2 and was associated with major secrets in later versions. In these appearances, RedXVI is generally grumpy and annoyed at the player for bothering him, a reference to his behavior in MADventure. While the character no longer appears in the game, his name is still used as a cheat code in v2.1.
In Demo 4, RedXVI is hidden in Castle Eggman Zone Act 2. To access Castle Eggman Zone, you must collect all seven Chaos Emeralds. If you do not want to play through all Special Stages, you can use a cheat code to obtain the emeralds: While in Techno Hill Zone Act 1, type
FISHDAKE on the screen (not the console) to be awarded a Chaos Emerald. Do this seven times to obtain all emeralds and then finish the stage. After clearing THZ1, you will then be warped to Castle Eggman Zone Act 1.
In act 2, jump into the pool in the center of the stage. The easiest way to do this is to get on top of the bridge that crosses part of the central room and jump from there. The pool has a gargoyle on each of its four sides except one. Go to the center of that side and you will drop into a hole in the floor of the pool. You will end up in an underwater corridor. At the end of it are three platforms that lead above the water surface. To the left of these platforms is another hole in the floor. After dropping down there, look around and you will see that one of the walls has an out-of-place texture. This wall is intangible. Behind it is a corridor with a spring that leads up to a small room above the water surface.
RedXVI stands in the center of this room. If you touch him, he will damage you and display the message: "That's for buggering me in my fangame, MADventure! Now sod off!" If you touch him again in less than 5 seconds afterwards, the game will crash with an error message that says "'User' did not understand 'SodOff_1'" and links to a now defunct download website for MADventure.
Red Volcano Zone (v1.09-v1.09.4)
An early demo of Red Volcano Zone Act 1 is hidden in the file
soar.dta but encrypted so that it crashes the game when loaded normally. To access it, follow these steps: First, complete the unmodified game three times. The game is considered completed upon beating Castle Eggman Zone Act 3, even if it was accessed via a save file or level select. Then, in Greenflower Zone Act 1, go to the plateau that contains the red brick house with Sonic's emblem on it. Jump on the house of the roof three times and RedXVI will appear in front of the door, asking: "Hey! Who's making all that racket?" If you touch him, he will call you out on disturbing his sleep and say "Go to hell!". After a few seconds, you will die and respawn in RVZ1. After completing it, you will be sent back to GFZ1 and may continue normally.
Note that while RVZ1 is accessible in netgames by the same method, the game will crash if a player joins while the map is RVZ1. To avoid this, adjust the player limit so nobody can join.
Black Chaos Emerald (v1.09.4 only)
An eighth Chaos Emerald is hidden in the game that allows Sonic to become Hyper Sonic, an even faster version of Super Sonic that kills all nearby enemies with every thok. To obtain this emerald, you must have collected all seven emeralds at least once and completed the Ultimate skill level (unlocked by completing Very Hard). Then, in Greenflower Zone Act 2, you must reach an area with another red brick house. It is located on the cliff to the right of the corridor with the brown fence near the start of the level.
There are two ways to get up there as Sonic. The faster but more difficult way is to collect the Super Sneakers at the start of the level and then use the spring in the first pond to the right to propel yourself towards the cliff. Alternatively, use the spring to get up to the area with the two moving platforms. Use these platforms to get to the top of the level. Continue forward along the narrow ridge you are standing on until the area with the first Star Post and the cave entrance is below you to your left. In front of you is the wall that stretches upwards from the cave entrance. To the left of that is another wall. Jump towards that wall and you will land on the cliff that contains the house.
Once you have reached the house, touch the door. You will find a note that says "Out to lunch". Now go back to the beginning of the map and use the red spring in the first pool to the right of the starting area to be propelled up to the cliff next to you. In the center of this area, you will see RedXVI having a picnic. If you touch him, he will give you the black emerald to make you go away. You will only retain the emerald for the current game, it will not carry over to other games or the unlockable level select.
God cheats (v1.09.4 only)
RedXVI's third appearance allows you to unlock the God cheats, which are called Pandora's Box in later versions of the game. To do this, you must have already collected the eighth emerald. Then, continue the game until you reach Castle Eggman Zone Act 2. Jump into the pool in the center of the stage (see the Demo 4 section for instructions). This activates the secret, and you will be alerted with an on-screen message. Now continue playing through the level normally. Before you finish the level, it is recommended that you get the Armageddon Shield, which is in the underwater corridor in front of the area where RedVI appeared in Demo 4 (in v1.09.4, it contains Sonic's emblem).
Now go to the area that normally contains the exit sign without losing your shield. The exit sign will be replaced by RedXVI who, after another rant, will teleport you to the area that contains Sonic's emblem. All your rings will be removed, and the room is filled with Crawla Commanders. If you have the shield, they will be damaged upon attacking you and you can easily kill them by spinning in place. Without the shield, you will have to start spinning immediately after being teleported or you will die. After defeating the Crawla Commanders, make your way out of the pool. The level will finish and you will be alerted that the God cheats have been unlocked.
In v2.0, RedXVI appears in Castle Eggman Zone Act 2 if you have collected all seven Chaos Emeralds. The gate at the start of the level will open and lead you right to the area with the path split. Use the spinning chain to propel you to the upper path. Continue along this path until you reach the revolving door after the cannonball room. You can find RedXVI in a small library room right next to the revolving door, dressed as a pope. If you touch him, he will apologize to you for his behavior in the previous encounters and declare that instead of sending people to hell, he now sends them to heaven. You will then be warped to Neo Aerial Garden Zone.
After completing Neo Aerial Garden Zone, you will be sent to Arid Canyon Zone Act 1 and can continue the game normally. The level will also become accessible from the secrets menu. If you encounter RedXVI again afterwards, he will give you 9999 rings and say; "I, Pope Rededict XVI proclaim AJ & Amy Husband & Wife on this day May 16, 2009". This is a reference to SSNTails' marriage, which prompted the release of v2.0.
In v2.1, RedXVI is used for a cheat code. If you type in
REDXVI on the title screen without opening the console, the secrets menu will appear (if it is not already presented) and the level select will be unlocked, along with the Sound Test and Play Credits features, which are always automatically unlocked with the secrets menu. Using this cheat marks the game as modified.