Someone should probably document all those monsters I've heard about! Well? Get to it! I'm certainly not going out there. Monsters are dangerous. <note important>This is only a list. For a non-Wiki of Lies catalogue (including descriptions too!) try this link. It's player maintained and publicly editable. All thanks to Rosemoo for making it!</note>

The List of Monsters On Improbable Island(In Alphabetical Order)

Admiral Flufferson

Ambush Hamster

Animated Aubergine

Army of Hippopotami

Atinlay Igpay

Bartender

Bats

Bear Tied to Back of Another Bear

Blonde Heiress

Bluebird of Happiness

Book of Riddles

Broadway Extras

Bumbling Ally

Car Insurance Gecko

Carrot Top

Cats and rats and elephants

Cereal Killer

Chili Chef

Chimpanzees

Crazed Tech Support Rep

Crazy Audrey

Creature From a Dodgy Anime

The Daughter of The Devil

Death or Cake Man

Delusional Blue Spandex-Wearing Lunatic

The Devil

The Devil in a Blue Dress

The Devil in some Darling Open-Toed Heels

Don of the Dead

Dopplegangers

Drunken Nudist

Dust Bunny

Everquest Junkie

Ferryman

Field Mouse

Fire-Breathing Kangaroo

Flying Spaghetti Monster

The Giant Tattoo Mutant

Golden Goose

Gordon the Cheese Eater

Gothic Romantic Heroine

The Government1)

Green alligators

Grunting Piggy

Haberdasher

Heart of Stone

Hiker

Huge Magnifying Glass

The Improbability Drive2)

Insane Proctologists

Invisible Man

Iron Chef

JerkyGangers

The Jerkymaster

Jesus the Pirate Ninja

Lex Luthor

Lions

Llamahawk

London Omnibus

Kentucky Fried Zombie

Kittens

Long-necked geese

Madness Duck

Malevolent Burly Man3)

Malfunctioning Rice Cooker

Man from deep, deep, dark, dark, deep, dark woods

Man from the Ministry

Mel Gibson

Member of Doktor Improbable Lovers Anonymous

The Mighty Magpie

Militant Pacifist

Octophant

Occam's Razorback

Old Crippled Beggar

The Other White Meat

Over-full Bookcase

Paper Tiger

Polar Bear

Pope

Potted Plant

Pretentious Jerks

Procrastination

Professional Romance Writer

The Psychedelic Mushroom of Eternal Chaos

Pushme Pullyew

Quest Monsters

Rabbits

Radioactive Dinosaur

Rank Ten Difficulty

Rap Scallions

Robots

Rude Duplicate Monster

Shady Trees

Shining Happy People

Skronky Rain

SKUB Activists

Sigmund Freud

Sinister Dexter

Slash Fanfic

Small Child

Small Piglet

Society of British Bedstead Men

Socktopus

Some humpty-back camels

Someone with caterpillars in their vagina

Someone's Grandfather

Sorority Girl in Nightie

Spiderkitty

Stonehenge

This Guy

That Guy

The Right Hemisphere of Your Brain

Thin Air

Thing from the Back of the Fridge

Three Toed Sloth

Tom Cruise

Tree4)

Ugly Harpy

The Undead Dreaming Catfish God

Ursa Minor5)

Vampires 6)

Velociraptor

Violins

The Watcher

The War on Improbability

Veteran Player

Winged Pistachio

Yet Another “Hitchhiker's Guide to the Galaxy” Ref

Your Mum

Your Own Tongue

your own trap7)

Your Future Self

Your Past Self

Your Present Self

your violent allergy to bullets

Zombie Puppy

Zombie Worm

1)
See evil
2)
Nonsense.
3)
Some monsters have “Lethal”, “Malignant”, “Savage”, “Deadly”, “Dangerous”, “Malevolent”, and “Elite” variants. These are have increased HP and are sometimes higher levels than their standard counterparts.
Monster levels range from 1 to 17.
4)
Level 17. I hate it.
6)
Not to be confused with Charm Vampires such as Seth and Emily
7)
sic