Alternate Universe SpongeBob- Appears in "Chimps Ahoy," when Patrick supposedly invented the already-invented mirror. He lives in the mirror, or in a parallel universe. His only line is, "Well, I thought it was a pretty good idea" after Patrick gets discouraged after he finds out that it was already invented. He speaks in a Ukrainian accent, a reference to the Ukrainian creator, Stephen Hillenburg. He also appears in "Wet Painters." His only line in that episode was, "You're on your own, pal." He also appeared in "Something Smells" in which he cracks his mirror after smelling SpongeBob's breath.
Helga - A female Viking who has only appeared in the episode "Dear Vikings." She was talking to Gordan when another Viking came, and interrupted "story time." She wears a silver Viking helmet, and has a Swedish accent.
Moe Blowfish - The host of a television show called "Fearless," he appears in the story book of the same name.
Iron Eye - Nickname of one of Mr. Krabs' navy buddies. His fake eye is actually made of Formica (plastic) seen in the episode "Shell of a Man." He is voiced by Tom Kenny.
Lockjaw Jones - Nickname given to one of Mr. Krabs' naval buddies. His teeth are different at the reunion compared to the teeth in the navy ("Shell of a Man").
Tentacle Acres Residents - A group of cephalopods who resemble Squidward, both in appearance and in personality. Squidward eventually became bored of them (Squidville).
Three Strong Men - Appears in the episode "Karate Island." SpongeBob thinks that he beats them up, but they are just pretending to make SpongeBob look good.
Gordon - the leader of the Vikings who appeared in "Dear Vikings." Ian McShane voices him.
Olafs - the Vikings, all named Olaf. Seen in "Dear Vikings." They are tall, muscular, bearded, and wear a Viking helmet. They all have Swedish accents. Even though they are all different, they all seem to have the same personality. If one of them says something that the others object to, they are catapulted off the ship.
Patrick Not-Star - A starfish SpongeBob mistakenly thought was Patrick. He lives in The End of the World and maybe related to Patrick Star.
Animals and Other Creatures
Worms are creatures that are a parody of dogs and live in Bikini Bottom. But there are also real worms along with them.
Alaskan Bull Worm - A giant pink worm, described as "Big, Scary, and Pink!," just like Patrick's belly button. It appeared in "Sandy, SpongeBob, and the Worm." It eats everything in its path. Sandy thought she could beat it up because it ate her tail. She teases SpongeBob into fighting the worm with her. It might be a parody of the Mongolian Death Worm.
Mr. Doodles - Mr. Krabs' pet worm. He was first shown in "Sandy's Rocket," but his name was first mentioned in "As Seen on TV." He is the undersea equivalent to a dog (just as Gary is equivalent to a cat).
Birdy - A bird who is one of Sandy's pets, who gets fed twice a day. Appeared in "Wormy."
Cricket - A cricket who is one of Sandy's pets, though in "To Save a Squirrel" there was a different cricket that was lost underwater. SpongeBob and Patrick thought it was a monster, which suggests they have a fear of certain land animals.
Snakey - A snake who is one of Sandy's pets. Eats mice.
Wormy - A caterpillar who is one of Sandy's pets. Befriended SpongeBob and Patrick in "Wormy." Wormy turned into a butterfly and caused a panic after the citizens of Bikini Bottom thought he was a monster.
Dog Who Speaks - Mentioned twice in "Patty Hype." He lives at the Shell Shack and can speak and sing. However, none of the townspeople know what it is.
Ducks - SpongeBob stepped on them, and said "Quack." There are three ducks. SpongeBob kicked one away at the end. They first appear in "Karate Choppers."
Jellyfish are creatures who wander around Jellyfish Fields. They "sting" other creatures by electrocuting them.
Big Lenny - A jellyfish from Bikini Bottom. He looks exactly like a normal jellyfish, but his skin is darker and he has an evil-looking face. He kills his victims by giving them fatal electric shocks. In "I'm Your Biggest Fanatic," it is revealed that Dr. Mannowar is the only known person to have survived an attack by Big Lenny, getting by with only a huge bump on his cheek that hurts when touched.
Evil Alien Jellyfish Overlord - A giant alien jellyfish that almost takes over Bikini Bottom in the episode "Planet of the Jellyfish."
Snails are creatures in Bikini Bottom and are a parody of cats. However, it has real snails too.
Mary - She appears in "Gary in Love" and Gary loves her. In the middle of the episode, she loves Gary. But in the end of episode when appearances Billy she loves him. She is very similar to Snellie and Mrs. Puff's snail.
Bad Guys - They are appeared in Gary in Love. Their name is unknown. They enters The Snail Park from back and their Leader loves Mary. He is enemy of Gary but end of episode they are friends.
Jerry - A realistic-looking snail pulled out of SpongeBob's pocket in ".
Lary - A pale purple snail adopted by SpongeBob to replace Gary in "Dumped." He has big bushy black eyebrows and a tan shell, as well as a rude and unpleasant personality.
Lightning Larry Luciano - An old, extremely slow snail with a mustache; appeared in "The Great Snail Race." He is snail racing's 1st champion.
Snellie - Squidward's pet. First appeared in "The Great Snail Race." She fails Squidward in the race and loses to Patrick's rock. She looks like Gary, only with blue eyes with long eyelashes, a pink bow and a pale blue navy and purple-spiraled lavender shell. At the end of the race, Gary falls in love with her. But she has so far not been seen again.
Rocky - Patrick's pet snail, whom he entered in "The Great Snail Race"; Rocky appeared to actually be a rock, but managed to overcome this setback to win the race. According to Patrick, he has "nerves of steel!"
Mrs. Puff's Snail - In the episode "The Sponge Who Could Fly," Mrs. Puff's pet snail is similar to Snellie. It is unknown whether that is Snellie herself, a different snail but with the same body color and shell color, given to Mrs. Puff by Squidward (this is proven false for Mrs. Puff claims to have had her since she was a little girl, and Squidward got Snellie in the series), a twin to Snellie, or if it's just a coincidence.
Large Snail - Seen in the episode "Nature Pants," this snail is a life-size gigantic blue-shelled snail appears and says "Meow," in the same way Gary does.
Black Snail - Seen in "One Krabs Trash" where it hisses angrily at Mr. Krabs in Floater Cemetery. A parody of a black cat.
Alley snails - A parody of alley cats, appeared in the episode "Have You Seen This Snail?," they are a gang of outlaw snails who like nachos, oddly, these snails were capable of speaking instead of meowing (although this may be what Gary is hearing). One snail got picked up by grandma.
Unnamed clam - In "Tea at the Treedome," this clam tried to eat Sandy, but Sandy defeated him with her karate.
Junior - The orphaned scallop adopted by SpongeBob and Patrick in "Rock-a-Bye Bivalve." Like other scallops, Junior has purple skin and a red tongue. He does not like Krabby Patties, donuts, or French fries, but he does like worms.
Shelly - SpongeBob's pet scallop. Not to be confused with the one from "Rock-a-Bye Bivalve." SpongeBob keeps him in a bird cage in his bedroom. His name was revealed in the SpongeBob: The Complete 1st Season DVD collection.
Magic Conch Shell - Seen in "Club SpongeBob." The Magic Conch Shell is a toy similar to a Magic 8-Ball; pulling its string will provide you an answer to your questions.
Clamu - Seen in "The Smoking Peanut." A Giant Clam capable of shooting a pearl 100 feet into the air. It was emotionally disturbed when Mr. Krabs stole its egg, claiming it was free day. The name Clamu is a parody of Shamu, one of the star attractions in SeaWorld.
Blue Lip - A giant clam that once ate Mr. Krabs' millionth dollar. In order to get it back, Mr. Krabs traded his entire body, except his head and his left arm. He appears in "Clams."
Pet Clam - SpongeBob's pet clam who lives in a cage in SpongeBob's room and is never mentioned or talked about.
The Little Guy - Mr Krabs' pet scallop in "Model Sponge." At the beginning of the episode, SpongeBob has mistaken the scallop for himself.
Moby Dollar - A giant dollar bill that Mr. Krabs wanted to catch while fishing. Appeared in "Sleepy Time" in Mr. Krabs' dream. The name Moby Dollar is a parody of Moby Dick, a whale in the classic tale of Captain Ahab.
Mystery - A wild green seahorse that likes to eat anything. Adopted by SpongeBob, but later set free. He wanted to name her "Grace," "Majesty," and "Debbie." She is voiced Frank Welker.
Sea Bear - A large animal with the body of a fish, claw-tipped fins, and the head of a grizzly bear. Appeared in the Camping episode. He kept beating up Squidward for random reasons. His weakness is a circle drawn on the ground. And the things you do to attract them is screaming like a chimpanzee, waving your flashlight back and forth (flashlights are their natural prey), stomping around (they take that as a challenge), wearing your sombrero in a goofy fashion, hoop skirts, or clown shoes, playing your clarinet, eating cheese.(Cubed, sliced is fine.)
Sea Rhinoceros - A creature with the body of a fish, and the head of a rhinoceros, these creatures are bigger and meaner than Sea bears and are attracted by sea bear attacks. The only known way to protect yourself from a sea rhinoceros is to wear anti-sea rhinoceros undergarments. Also seen in "The Camping Episode."
Lion Fish - A creature with a head of a lion and a body of a fish that loves sausages. It is seen in "Spongicus"
Sea Urchin - Appears in "Nature Pants." Coming in contact with them causes itching, similar to poison ivy.
Unknown Species (a.k.a Smellies) - Unknown species called smellies (because of Squidward's name at the time,) who were briefly seen in the SpongeBob episode "The Thing." They look a lot a Pikmin, a Nintendo GameCube game characters and Bloo, of Foster's Home for Imaginary Friends, with muffled voices, Squidward-like eyes and noses, tiny round mouths, large bulbous cheeks and furry, cement-colored bodies. They love jazz music.
Two clams - Appears in "Born to Be Wild." SpongeBob and Patrick goes in one's mouth to hide away from the "wild ones," but he didn't like the taste of SpongeBob and Patrick so he threw them out of his mouth and drinks some water. The other clam asks "Hey! What happened?" The clam that threw SpongeBob and Patrick out of his mouth replies "I don't want to talk about it."
Kelp Forest Bug ("Club SpongeBob") A very small bug that Squidward cooks in a frying pan until food falls from the sky for SpongeBob and Patrick. When Squidward's jaw drops, the bug jumps out of the pan and hits Squidward on the head with a stick.
Undersea Fly - Much like normal flies, they are normally seen around dumpsters, trash cans and anything smelly.
In the episode "A SquarePants Family Vacation," SpongeBob and Patrick fall into a ravine filled with mushrooms and Red Kelp. Among the creatures who live there are very strange and unnamed, and are similar in many ways to other trench dwelling creatures from the SpongeBob Movie and the episode "Rock Bottom."
A Giant Fruit Fly that stalks the duo.
A small, loud bellowing animal that mimics a horrifying sound and scares SpongeBob and Patrick into running away.
A beaked monkey that follows the two during their road song.
A Two headed centipede that also follows them during their song.
Three aquatic flower beings, yet again followers of the Road Song.
A burrowing rabbit fish that follows them during the song as well.
Three turtle like creatures with rocks for shells. Two of them follow SpongeBob and Patrick, while the third one puts out a 'Do Not Disturb' sign after the others depart.
A giant blue anemone of which the two bounce off of during their accidental fall from a cliff while avoiding the bellower.