The Player Character
Yes, the player character, aka you. The one who goes around to solve all the islands' problems, saves Poptropica on a regular basis, and travels around in a blimp. Can be a boy or a girl.
Badass: Fights baddies on a regular basis, travels through space, saves Poptropicans daily, tracks down artifacts, and that's only the tip of the iceberg.
Badass Normal: Since Poptropica is a Fantasy Kitchen Sink with super-powered people, Greek gods, vampires, medieval royalty, zombies, etc., and the player character is more or less a normal Poptropican, you're this as well.
Empowered Badass Normal: A variation. The player character can gain powers on certain islands (such as Super Power Island), but said powers are always limited to only those islands.
Flight: In Early Poptropica, you find a jetpack in the airplane graveyard, and in Super Power Island, the retired superhero gives you the power of true flight in order to help you take down Betty Jetty.
Heroic Mime: Averted. You can talk to other players (albeit through pre-recorded questions/responses like "Can you juggle?" and "Do you want to play head-to-head Paint War?"). You also talk to NPCs, and to yourself in some cases (e.g. "I don't think Snoopy has much to say").
Parental Abandonment: His/her parents are nowhere to be seen. The only mention the player character ever makes of them is on Back Lot Island, if you click on the chocolate-flavored soap sud bottles in the MacGuffin's store:
Player Character: I wish my mom would've washed my mouth out with these.
Powerpuff Girl Hands: Like all Poptropica characters, your hands are simple spheres with no fingers.
Purely Aesthetic Gender: There are literally no differences whatsoever between the player character being a boy or a girl.
Unwitting Pawn: Ends up being manipulated by island villains on more than one occasion; Spy Island, Counterfeit Island, Mythology Island, and Super Villain Island being prime examples.
Early Poptropica Island
A colony of Poptropica's first settlers, who have several vital possessions stolen (a pig, water bucket, and flag). The island quest is to get the items back to them.
Non-Standard Character Design: Their designs are much more pixelated than the average Poptropican, and each of them have a clearly defined black outline.
One-Gender Race: Not as bad as other examples, since only about six are shown, but the ones who are seen are all male.
A giant who lives in the clouds in the sky, who has his club set down to prevent you from passing through to find the water bucket. To make him lift his club, you have to find his missing golden egg in the sewers and bring it to him.
The Faceless: The only parts of his body we see are his feet.
Shark Tooth Island
An islander who wears a dark blue mask and lives on a stand with a straw roof on top of a palm tree. He only helps you out if you are wearing the grass skirt that the salesman gives you, and instructs you to go to the temple to find the ingredients he needs to brew the potion that will tame the Great Booga Shark. Once you bring him the needed ingredients, he brews a potion in a coconut that you need to launch with the coconut cannon to feed to the Great Booga.
Cool Mask: He has one that covers his entire face, which even has shark teeth decorated around the mouth.
A mysteriously vanished professor, who disappeared during his studies of the Great Booga Shark. He turns out to have been trapped on an island by the Booga along with a young boy. After you put the Great Booga Shark in a deep sleep with the potion, you are able to go to the island to lead the Professor and the boy back to mainland. As thanks, the Professor gives you the island's medallion.
Posthumous Character: Seems to be this. Subverted, in the end he's revealed to have been alive and stuck on an island.
Great Booga Shark
The "villain," so to speak, that swims around the island and prevents the natives from going out into the sea. When you give it the potion in a coconut that the Medicine Man brewed, it sinks to the bottom of the ocean in a heavy sleep.
Future Player Character
The player character from fifty years into the future, who warns you about the bad future s/he comes from and gives you the time device needed to go back in the past to repair it.
Future Me Scares Me: Averted. The player character's future self isn't seen as very irritating or freaky, and is more or less the same person (as much as you can get in-game, anyway), only with bags under his/her eyes, white hair, and a pack of sticks on his/her back when coming from the Bad Future (but with glasses at the end, when you meet with him/her again).
The Big Bad of the island, as well as Poptropica's first proper villain. He is the reason behind the carrot deficiency, having brainwashed many citizens into bunny drones that work for him and help make the stolen carrots into fuel for his robot spaceship (a "rabbot").
The owner of the local comic book shop, who gives you a guide on becoming a superhero. At the end of the quest, he barges in at the last minute and punches out Betty Jetty for you. Because of this, he's the one who's given the island medallion instead of you, though he gives it to you anyway in exchange for a hot dog.
Flight: The only villain on the island who can fly.
Rose-Haired Girl: She has light pink hair, but doesn't fit any of the character types associated with it.
The director of the secret agent organization, who entrusts you with the mission to rescue the three missing secret agents and stop B.A.D., a notorious criminal association that uses lasers and a satellite to zap off the hair of Poptropicans all over the island. It turns out that his "hair" is actually a toupee, and he's the mastermind behind B.A.D. Once defeated, he is imprisoned in a cage in the agency building.
Bald of Evil: His "hair" is really a toupee to cover up that he's bald, like all the other members of B.A.D.
Walking Spoiler: It's near impossible to discuss him without spoiling the fact that he's actually the Big Bad of the island.
Would Hit a Girl: In the climax of the island, he does his best to take out the player character, regardless of their gender.
The Three Secret Agents
The three top agents of the organization, who have gone missing and are in need of rescue. Once you save each of them, they give you things that come into great use during the quest.
Distressed Dudes: The two male agents, one being tied up in a room at the docks and the other being tied up in an attic.
Faux Action Girl/Faux Action Guys: All three of them. Though they're stated in the island's description (when it was still in development) to be the best agents, all they do are get held hostage and, upon being rescued, give you important objects (the laser pen, grappling bow-tie, ultra-vision goggles, and satellite clue cards altogether) before running away.
Big Nate Island
The daughter of the King and Queen of Arturus, who was kidnapped during an attack on the castle by space invaders. She had a keen interest in space, and was a member of Mordred's Secret Order. It's revealed that she was trying to communicate with Mordred from his whereabouts in space, and was kidnapped after she sent him a signal from her tower. She is revealed to be trapped in a green prison in Mordred/Binary Bard's fortress. Once you defeat Binary Bard, she is released from the prison and saves the Orb by punching out the Binary Bard so you two can escape.
Badass Damsel: At the end, when you defeat Mordred and the Orb drops out, he comes out to claim it, but the princess, now free, jumps down and punches him. The punch is enough to knock him out and give you two the chance to escape with the Orb.
Brainy Brunette: She appears to have been quite intelligent and studious, if her star charts and many papers in her room are any indication.
Damsel in Distress: She's already taken away by space invaders by the time the island starts, and spends most of the quest being held hostage by the Binary Bard.
Princesses Prefer Pink: Played with. Her outfit isn't pink and is instead green with gold trimmings, but her bedroom is completely decked out in pink.
The Three Knights
Three knights who were sent to rescue the princess after she was abducted, but never returned. Each of them is on one of three planets (Jungle, Fire, and Ice). Their names are Sir Cador, Sir Pelleas, and Sir Gawain.
An inventor who was famous for making many creations that improved the kingdom, but was imprisoned when he started going too far. He broke out of prison by escaping in a spacecraft he made himself and hasn't been heard from since. He's actually still alive and now resides in his own realm out in space, and was the one behind the Princess's kidnapping. To survive, he added metal parts to himself and now calls himself the Binary Bard.
And I Must Scream: At the end of the Astro-Knights Island quest, when the Orb is taken from him, he's left trapped in his own realm with no way to escape.
Evil Costume Switch: When pretending to be a Reasonable Authority Figure, she has neatly styled black hair and wears a suit. After she shows her true colors as the Black Widow, her hair is in untidy spikes and she wears an entirely black outfit with a red hourglass shape.
I Have Many Names: According to a newspaper article, she's also known as the White Widow, the Sand Spider, the Twilight Tarantula, the Creepy Crawly Canvas Criminal, the Evil Eight-Legger, the Art Appropriating Arachnid, and the Thief with a Thousand Names.