The cast of the Ghost Suburb games. Spoilers are unmarked.

Protagonists

Nurse Okay

"Sleep. I must find it. This graceful rest I once had, so that dreams may come and dance in front of my eyes."

The heroine of Ghost Suburb II. She is an overworked and insomniac nurse who wants to sleep.

Deadly Doctor: Nurse Okay, as the protagonist, is capable of fighting against all manner of strange monsters, and her attacks all have names related to medical care and surgery.
Hospital Hottie: She is a nurse and is attractive, enough for the married Dr. Leads to start an affair with her.
The Insomniac: She has not slept in four months, and her goal throughout the game is to discover why that is.
It's All My Fault: The reason why Okay can't sleep is because she blames herself for Sleep becoming braindead because of her.
- Or so she thinks, in truth she was trapped by Gertrud in a dream as revenge for sleeping with her husband. In the True Ending, Okay kills her, hoping her insomnia will end at last....only to find out Insomnia and Narcolepsy were working with Gertrud and continue where she left, thus keeping Okay insomniac forever.
The Mistress: Was this for Dr. Leads, who was already married to Gertrud.
Only in It for the Money: She agreed to sleep with Dr. Leads cause she's not doing well financially.
The Shut-In: She doesn't leave her dorm room in the hospital much (or at all, according to Gertrud).
Who Names Their Kid "Dude"?: Okay lampshades her name in the beginning of the game.
"That's my name, it's an odd name but that's what everyone has asked me forever, so I assumed that was it."

May

The heroine of Ghost Suburb Zero.

Instead;Ghost Suburb Protagonist

The nameless girl who is the protagonist of Instead;Ghost Suburb.

Big Bad: Of Instead;Ghost Suburb, which follows her killing the villagers and sacrificing them to the shrine.
Generic Doomsday Villain: Rare Villain Protagonist variant, but since she never speaks, it is never made clear why she is sacrificing the villagers to the shrine.
Spree Killer: The game concerns her slaughtering the residents of a village over a single night.
Villain Protagonist: She is the Big Bad in Instead;Ghost Suburb, since you play as her killing innocent villagers.

Major Characters

Gertrud

"See- feel me, touch me... I am real. You just need to sleep you damn creep."

A floating eye who claims to not be an eye. She hangs around Okay but annoys her a lot.

Battleaxe Nurse: She is a nurse who is also a Wicked Witch, cursing and ruining the lives of Dr. Leads and Nurse Okay for cheating on her. She also has no care for the test subjects of the hospital, as she sabotaged the experiment with Sleep, rendering her brain dead, as part of her plan.
Big Bad Duumvirate: She works with Insomnia and Narcolepsy to ruin Okay and Dr. Leads for cheating on her, and trapped Okay in a nightmare. They turn on her, but she continues to be a threat in the waking world when she tries to strangle Okay to death.
Cute Is Evil: Her true form is that of a small, adorable green-haired girl who is vicious enough to turn her husband into a monster and trap Okay in a nightmare as revenge for infidelity.
Deal with the Devil: She made a deal with Insomnia and Narcolepsy to transform Dr. Leads into a monster and torment Okay. But eventually the latter two decide they have no use for her and kill her dream self.
Fairy Companion: She is a floating eye who serves as Okay's partner throughout the game. Until the end of the Disc-One Final Dungeon, where Sleep hijacks it instead.
Rape by Proxy: After transforming Dr. Leads into a monster, she has him rape Okay, his mistress, as revenge.
Wicked Witch: She is said to be a powerful witch and is working with Insomnia and Narcolepsy to trap Okay in a never-ending nightmare.
Woman Scorned: Dr. Leads cheating on her with Okay is what drove her to ruin their lives.

Sleep

A mysterious entity who is frequently mentioned.

Big Good: She turns out to have been watching over Okay and, when she makes her entrance, she guides Okay through the rest of the journey, helping her take on the Big Bad Duumvirate.
Fairy Companion: She hijacks the eye avatar that Gertrud uses at the end of the Disc-One Final Dungeon.
Good All Along: Gertrud treats her like a malicious entity and says she is the reason Okay can't sleep, but she never harmed anyone and is actually trying to help Okay.

Dr. Leads

The head scientist of the secret government experiment.

Asshole Victim: He cheats on his wife and uses Sexual Extortion to make Okay into The Mistress, and is callous with his patients. So when his wife, Gertrud, turns him into a monster, it is at least somewhat understandable.
Forced Transformation: Gertrud turns him into a monster with tentacles covering his face.
Jerkass: He cheated on his wife with Okay, gave her the job in exchange for becoming his mistress, and is part of a secret government experiment on people with special powers. He also callously pushes Okay out of the way and tells her to leave when the Sleep experiment goes wrong.

Insomnia and Narcolepsy

A pair of entities that brought about Okay's nightmare.

Amanda Panda

The shopkeeper character who wears a panda suit to entice customers to buy her stuff.

Mr. Operation

"They call me Mr. Operation- I don't think I've ever seen you before, Nurse Okay!"