Debug Room

The Debug Room is a secret area only accessible after defeating the Creator in the Sanctuary, ordinarily blocked off by him. In it, the player can do such things as see sprites (both used and unused), buy a large number of items, edit levels and money, activate the King Crimson feature (which allows skipping cutscenes and opens a medicine and weapon shop over the Radio), change the Stand and appearance of the player character, and read original character profiles. Nearly every area in the game can be revisited, and character endings are viewable.

After clearing the game 6 times or more, the pig in the toilet will have a door behind it, leading to a room where the original Stand sprites. After 11 or more Repeat Playthroughs, you will be able to change your gender by talking to Anasui, Clayman's true form is unlocked, and Vins will appear in the room. If she is talked to after obtaining the Succession End, you will be able to go to the Dream World.

Party Members
The Debug Room allows you to recruit any party member that can be recruited in the game. These include... In addition, you can change any of your normal party member's FP, and even remove them from your party.
 * Speedwagon (AI controlled)
 * Dire (AI controled)
 * Straits (AI controlled)
 * Stroheim (AI controlled)
 * Lisa Lisa (Player controlled)
 * Caesar (Player controlled)
 * Messina (AI controlled)
 * Loggins (AI controlled)
 * Zeppeli (AI controlled)
 * Gallahad (AI controlled)
 * Miriam (AI controlled)
 * Senator Wilson Philips (Player controlled)

Teleportation
By far one of the most interesting bits in the Debug room, the Teleportation Room the player arrives in allows you to teleport to almost any point in the game. In addition, you can watch the special endings for your party members. All doors are denoted by a translucent sprite, resembling either an enemy stand or a party member. The teleportation are as follows.
 * The hotel in Hong Kong (Silver Chariot door)
 * The hotel in the harbor (Dark Blue Moon door)
 * The ghost ship (Strength/Ghost Ship door)
 * The hotel in Singapore (Ebony Devil Doll door)
 * The hotel in Singapore, post-Devo fight (Yellow Temperance door)
 * The train to Calcutta (Hanged Man door)
 * Varanasi (Empress door)
 * The Wheel of Fortune ravine (Wheel of Fortune door)
 * Justice's town (Justice door)
 * The rest stop outside of Karachi (Lovers door)
 * Karachi (Sun door)
 * Death 13's Dream World (Death 13 door)
 * The deserted island (Judgement door)
 * The submarine (High Priestess door)
 * The Fishing Village (Geb door)
 * Aswan (Vins door)
 * The hospital in Aswan (Thoth/book door)
 * Kom Ombo (Anubis/sword door)
 * Edfu (Bastet/electric outlet)
 * The hotel where Sethan appears (Alessi with Sethan door)
 * The telephone booth in the desert (Osiris door)
 * Cairo (Horus door)
 * Cairo after Dio's mansion has been found (The World door)
 * The Speedwagon Foundation hospital (Stroheim door)
 * The Sundarbans (Speedwagon door)
 * Charlie Rich's mansion (Submarine door)
 * Saudi Arabian beach (Judgement door)
 * The underground library in Dio's mansion (Vins door)

Note that using any of these doors will increase Jotaro, Joseph, Abdul, Kakyoin, and Polnareff's level by an amount (depends on which door is used, Hong Kong and Harbor doors will not increase Polnareff's level), set bad karma to 0, and rewind the day counter back to 0.

Events

 * Changing the Music
 * Talking to Akira will allow the background music to be changed to another track. The list of songs available are:
 * "Jojo's Bizarre Adventure"
 * "Stardust Crusaders"
 * "100 Year Bond"
 * "Theme of Jotaro"
 * "Theme of Kakyoin"
 * "Theme of Joseph"
 * "Theme of Abdul"
 * "Theme of Polnareff"
 * "Theme of Iggy"
 * "Justice Will Prevail"
 * "Wicked Charisma"
 * "Vampire"
 * "Wild Dance"
 * "Face-Off!"
 * "Proud Warriors"
 * "Head-On Conflict"
 * "Overdrive!"
 * "Clashing Power"
 * "Dio's World"
 * "20m Radius"
 * "Help Has Arrived!"
 * "Cyber Terrorist"
 * "The Aloof Stand User"
 * "Bonds Of Destiny!"
 * "Beauty Of The Orient"
 * "Southeast Asian Journal"
 * "Southern City"

Talking to Dio will allow you to fight him and The World. He drops a Phantom Blood after being defeated, and may drop a Badge of Honor. Talking to the man in the same room as Dio will give the option to refuse to come back later. Choosing "Fight him anyway" to the question after this will begin an extremely difficult fight against Hirohiko Araki (with the sprite of Rohan Kishibe). Araki will periodically summon enemies (by drawing them) in order to increase the fight's difficulty: Dio Brando, Cars, Kira, and Diavolo. If one manages to defeat Araki, they will be rewarded with a Badge of Honor.
 * Against Dio
 * Against the mysterious manga artist

As well, every time you defeat Araki, the game increases a hidden counter by 1. If you do not have the Ultimate Debugger in your inventory, the game generates a number from 0 to 999 and checks if the number of times you defeated Araki is greater than or equal to the generated number. If the counter is greater than or equal to the generated value, the Mysterious Manga Artist will give you the Ultimate Debugger. Talking to Clayman will give the option to fight her. Since HP and SP are restored every turn, the fight is more for practice. After 11 or more Repeat Playthroughs, Clayman's true form is unlocked.
 * Against Clayman

Game-Changing Aspects
Talking to certain characters will allow you to change fundamental aspects of the game.
 * Rohan - Will use Heaven's Door to let you gain levels.
 * Okuyasu - Will use The Hand to erase your levels.
 * Keicho - Will use his Stand arrow to give you a new ability, from the pool of abilities that can be earned from Badges of Honor, either through a new skill, or by asking Judgement for a new skill. However, he can only give you the 34 skills listed on the first chart, not the 11 skills that are listed on the second chart (for example, he cannot give you Shockwave or Penetrating Glare).
 * Akira - See above
 * Kira - Can turn back one day with Bites The Dust. Note that to exit the Debug room, you must go through one of the Teleportation doors, which already rewind time to Day 0, so this is mostly a moot point.
 * Aya Tsuji - Will use Cinderella to change your appearance and Stand.
 * Koichi Hirose - Can lower or raise the encounter rate.
 * Josuke Higashikata - Completely restores your party's health and SP.
 * Shigekiyo "Shigechi" Yangu - Can give you any amount of money, up to 999,999G.
 * Giorno Giovanna - Gives you King Crimson for free. This is a very good offer, due to the fact that King Crimson is normally only availiable for 3 Badges of Honor in the Developer's Room.
 * Enrico Pucci - Will remove Ripple and Stand skills learned from books, the arrow or Badges of Honor.
 * Holly Kujo - Can remove all party members and check friendship levels. Also gives total FP, and says that the Senator Wilson route requires a total of 40 FP.
 * Bartender - You can buy whiskey from him for 100G
 * Sandbag - Can fight anywhere between 1-10, who do not attack. Useful for testing new abilities and achieving Bags of Sand.

Miscellaneous Tidbits
There are still several more characters in the Debug room, but they only provide flavor text. By room...
 * Every single original character Stand user, located in the Bar. Talking to them will give you a lengthy explanation about who they are and what they do.
 * Diavolo is in a filthy room. Talking to him will prompt your character to slay him. This erases him for some time, but he comes back rather quickly.
 * Buccellati, Narancia, Abbacchio, Mista, Fugo, and Trish are in a small room next to Diavolo.
 * Foo Fighters, Emporio, Weather Report, Anasui, and Hermes are in the room next to the above. Talking to Emporio's computer will allow you to use the Stand Summoning Program minigame. Talking to Hermes allows you to accept her panties.
 * Clayman, Clayman's Husband, Clayman's children, and a cat are in the room next to the pig toilet. Talking to Clayman's Husband with Cheats enabled will have him give you 99 of every stat-boosting item.
 * Caesar, Young Joeseph, Messina, Loggins, and Lisa Lisa are in the room directly above the stairs to the sprite room.
 * Yoshihiro Kira, Mikitaka, Enigma Boy, Yuuya Fungami, and Hayato Kawajiri are in the room next to the above, and above Clayman and her family. Talking to Hayato allows you to to decide whether or not to put a hat on him.

Ultimate Debugger
After facing and defeating True Clayman she will give you the Ultimate Debugger. The Debugger is able to do the following by accessing it through your menu: You cannot use the debugger in battle.
 * Fully recover Health and SP instantly
 * Raise or lower your level
 * Learn a random arrow skill
 * Max out your money
 * Change what Day it is (Ex: turn Day 42 to Day 17)
 * Change your FP
 * Toggle King Crimson
 * Stock Status up item
 * Warp directly to the Debug Room

Trivia

 * Each debugging game-altering character is a reference to the respective characters or their abilities in their canon:
 * Rohan is able to use Heaven's Door to grant skills to others, so he can grant levels.
 * Okuyasu uses The Hand to erase objects, so he can erase your levels.
 * Keicho possesses a stand arrow, so he can give random new abilities.
 * Akira is a musician, and can change the background music by playing a new one.
 * Kira can reset time with Bites the Dust, so he can reset the day counter.
 * Anasui was initially drawn as a female in Stone Ocean before later being drawn as a male, so to reference this, he can change your gender.
 * Koichi can lower or raise encounter rate by using Echoes' sounds to attract or repel enemies.
 * Josuke's Crazy Diamond can fix objects, so he can restore your party's health and SP.
 * Shigechi's stand Harvest is used to gather money, so he can give you infinite amounts
 * Giorno is an exception, since he does not wield or grant the actual King Crimson, but he was likely chosen since Diavolo only appears as a boss.
 * Pucci can grant or remove abilities with Whitesnake, so he can remove your abilities.