Finn Mertens

"Mathematical!"

- One of Finn's catchphrases

Finn Campbell Mertens (simply known as Finn and formerly known as Pen in the original short) is the main protagonist of the Cartoon Network series Adventure Time.

Appearance and equipment
Finn is a 12-year-old human. He has very thin, noodly limbs. He has several missing teeth because he bites trees and rocks among other things.

Although his eyes typically lack detail and appear as small black dots due to a minor mutation, they are shown to have color in the episode "The Enchiridion!," when Finn is tried by the Dark Magician. His left eye is green while his right eye is blue, characteristic of the genetic condition heterochromia. (But as stated by Andy on Formspring, "That was a special occasion. The heterochromatic effect was a byproduct of him being hypnotized by that guardian dude." Andy Ristaino confirmed that Finn's eyes are blue.

Hair
Finn has blonde hair which can be seen in "To Cut a Woman's Hair," where Finn removed his hat, and long, golden locks of hair flowed out. His hair had a glowing sheen and extended his body length, until he cut it off and gave it to the Tree Witch. His hair subsequently began to regrow, as shown in "Mortal Folly," "Heat Signature," "Apple Thief," "Beautopia," "No One Can Hear You," "Another Way," and "Beyond this Earthly Realm." In "Beyond this Earthly Realm," Finn's hair was shown to have grown past his shoulders and in "Gotcha," LSP's vision of Finn shown that his hair had grown down to his waist.

Clothing
Finn wears a white hat with two "ears" sticking out on top. The hat is inspired by Bueno the Bear, a bear that appears in comics made by Pendleton Ward, the creator of Adventure Time. He has proclaimed it to be "awesome." Finn's hat is bear themed; coincidentally the Hyoomens wear animal themed hats as well. This might be a hint that humans in the Land of Ooo wear animal hats to fit in the society. Finn's hat covers his entire head except for his face. He also wears a light-blue T-shirt, denim shorts, a green backpack, rolled-down white socks, and a pair of black shoes. In "Ocean of Fear," his footwear appears to be black booties with white cuffs. In "It Came from the Nightosphere," Finn had a small pocket sewn onto his shirt that he carried Jake in. When he's in the Ice Kingdom, he occasionally wears a yellow sweater, but has also recently worn his pink sweater made by Princess Bubblegum. In "In Your Footsteps," Bear wears Finn's clothes, which may mean that Finn has multiple sets of the same outfit, along with multiple hats.

He wears white briefs that made an appearance in "City of Thieves" when Penny stole his trousers at the end of the episode.

Finn sleeps in red footie pajamas that have appeared in many episodes, but in the Animated Short, he sleeps in a red sleeping bag in his regular clothes. In the series, the sleeping bag is beige.

Weapons
Although Finn has wielded a number of weapons, he originally favored a gold sword. As of the episode "Mystery Train," Finn is shown using a new sword with a pink/silver blade and a red, twisted "root" handle. (Finn's original sword was destroyed by a black hole in "The Real You.") Along with his new root sword, his green backpack has a new side strap that can hold the sword while Finn is walking. In the episode "Dad's Dungeon," Finn and Jake ventured into Joshua's Dungeon, which was built by Joshua to toughen Finn up. In the dungeon Finn retrieves Jake's family sword, which has replaced the Root Sword as his primary weapon. In the episode "Play Date" the demon Kee-Oth took the blood which was his from the sword back into his body while taking jake. The demon blood sword gets filled with blessed grape juice in "The pit". In the episode "Blade of Grass" finn trades his demon blood sword for a one made out of grass. Later in the same episode the blade attaches to his arm. After fighting a grass wizard Finn has accepted his fate with the sword and has learned to control it.

In "Conquest of Cuteness," Finn was shown to have a crossbow. He used a different one in "The New Frontier."

Personality and character traits
Though at times violent and aggressive, Finn is a brave and righteous hero. He has a very strong sense of responsibility and gets upset when he is unable to help others. He is almost physically incapable of doing anything evil or unjust, and will struggle greatly against doing such things, as seen in several episodes such as "City of Thieves," "The Eyes," and "The Enchiridion!" Even though he acts like a normal boy, Finn acts like a gentleman when it comes to ladies.

Finn is shown to be a fearless thrill-seeker and enjoys putting himself in the midst of danger simply because he enjoys a challenge. However, as illustrated in "Ocean of Fear," Finn has an unexplained phobia of the ocean, or thalassophobia, which may be explained in a future episode, despite the fact that he can effortlessly come into contact with any other body of water. While he portrays himself as a rough and tough hero, Finn has a tender side capable of love and compassion, as shown by his boyhood crush on Princess Bubblegum and his brotherly relationship with Jake. However, Finn seems to hate romance movies and kissing because in "Go With Me," he actually vomits during a kissing scene in a movie. But at the end of "Dream of Love," Finn was not grossed out by Tree trunks and the pig kissing.

Finn’s aspirations to be a great hero makes him somewhat of a moral sheriff in the Land of Ooo, as he is willing to help and protect any innocent person or creature. Finn appears to be somewhat simple-minded, seeing that he gets a lot of conflicting emotions when it's unclear whether something is good or evil (exemplified by his dealings with Marceline in the episode "Henchman").

Many aspects of Finn's personality are shrouded in mystery. In the episode "Rainy Day Daydream," it was shown that Finn believes "imagination is for turbonerds who can't handle how kick butt reality is," showing Finn not only accuses imagination users as turbonerds and believes life is fantastic. Finn then refused to use his imagination until he had to reactivate Jake's "bombastic personality" in his imagination land, (which was just a basic gray and white empty plane hinting that Finn isn't very imaginative but that was contradicted in "Power Animal" when the gnomes harnessed the energy from Finn's imagination) which was inhabited with a few dainty creatures such as Bellamy Bug who represented Finn's secret desire to be civilized (that he will not admit to). Finn's imagination was than powerful enough to effect the real world (like Jake's but to a lower degree) and turn on Jake's imagination.

Finn can occasionally be a little self-centered such as in "Freak City." Finn can also be very stubborn, such as in "Memories of Boom Boom Mountain," "Rainy Day Daydream," and especially in "Another Way." Finn can also be easily tricked, as in "The Eyes" when Jake convinced him that the giant hawks would take the horse to a land of sunshine and love stuff and take care of him. He can get overly angry and yell as in "Trouble in Lumpy Space" and "Tree Trunks," but he immediately feels guilt and remorse and apologizes when he can. Finn prefers to do work and not take the easy way out ("Business Time").

Physical
Finn is proficient in several forms of combat, including hand-to-hand combat, magic, and swordsmanship. He can jump very high and is exceptionally strong and agile for a boy of his age. Despite his age and appearance, Finn seems to be quite strong and athletic; he can be seen wrestling full-grown Marauders, the large grass ogre Donny, and a general variety of monsters and creatures several times his size. Finn is also capable of lifting up Princess Bubblegum, as shown in "Mortal Recoil" when he picks her up and puts her in her bed, and capable of lifting up Marceline as seen in "Daddy's Little Monster." He also can make his arms and legs bend in inhuman ways, as during the Science Dance and when he uses "spaghetti limbs" (waving his arms and legs, which Jake can also do). In "The New Frontier," it's shown that Finn can make fire only with his hands.

Mental
Finn has the ability to mentally fight psychic abilities. The first time was against the Lich. The second time was against Goliad, as he was constantly able to manipulate his thoughts in order to avoid revealing the plan to defeat Goliad, allowing Princess Bubblegum to create Stormo. As demonstrated in "The Creeps," Finn can lock unwanted memories in "the vault." However, this is a normal human ability which is activated if the scene the person had witnessed is too traumatizing for them. Finn has the ability to read and write, and he can also do simple math.

Creative
Besides combat, Finn has displayed many other impressive abilities in handicraft. He has some origami skills, as shown in "Ricardio the Heart Guy," in which he makes Princess Bubblegum a paper crane, as well as in "Marceline's Closet", in which he makes a paper airplane. In addition to that, Finn is shown to be able to construct a sculpture (of the Candy Kingdom) from his saliva, which was also made for Princess Bubblegum in The Real You. Finn is also somewhat gifted at constructing simple machines, such as the catapult in "The Witch's Garden." Finn writes and draws with his left hand and occasionally with both hands at the same time. He additionally handles his sword with his right hand, suggesting he may be ambidextrous, able to use both hands with equal skill.

Musical
Finn enjoys singing; after swallowing a tiny computer, he gained the ability to Auto-Tune his voice on command, although he can sing without auto-tune as well. Apparently, Finn can also play the flute, demonstrated in "Prisoners of Love," in which he played a short lick before javelin-throwing it at Ice King. Unfortunately, the flute fell apart before it could hit him, Finn has not played the flute in any episode since, this is probably because of it breaking. He is also very good at beat boxing. In "Gut Grinder," Finn tries to play Jake's viola, but Jake says he stinks. Jake even imitates his foot prints and said "I'm Finn the human and I stink at viola." However, during "Death in Bloom," Finn panicked over what instrument to pick, supposedly because he could not play any of them, and settles for sleigh bells. In the episode "Go With Me," Finn is seen playing the lute.

Miscellaneous
Finn is very good at playing a video game called Adventure Masters, which he and Jake play on BMO from time to time. He can also spit very long distances, as demonstrated in "Evicted!," when he spits on Marceline, in "My Two Favorite People," when he spits on Tiffany's face, and in "Web Weirdos", when he spits at birds flying overhead, while suspended upside down on a giant spider web. In "Dungeon," one of the trials that Jake says Finn would have breezed through is a spitting competition against a goblin-like creature. In "Burning Low", Finn is shown to be able to spit water incredibly high into the air.

Temporary
Finn and Jake gained magical abilities in the episode "Wizard," but they have never used those abilities in any other episode. Pendleton Ward later revealed on his Formspring that all of the magic Finn and Jake gained in that episode was contained in their robes, which were destroyed.

Likewise, in "The Chamber of Frozen Blades," Finn and Jake gain ice-ninja skills, but it's unlikely they will use them again because, according to Adam Muto, "They didn't have enough time to commit the incantations and hand positions to memory."

Past lives
Many years ago, Finn was a massive comet known as the Catalyst Comet that hit the Earth. It is not known whether he was one of the previously seen comets or a separate incarnation. Years later, he was reborn as a blue butterfly, and then a strange blob-like creature (probably a candy elemental). He was then a humanoid girl name Shoko, who was horribly mutated before her death. Finn completes her dying wish by returning Princess Bubblegum the amulet that Shoko had stolen from her in the past.

Age
Finn was 12 years old at the start of the series and is progressively getting older. As of "Mystery Train," he turned 13 years old. Finn is shown going through puberty throughout the series. This is seen whenever when he's screaming - his voice cracks. Finn's voice is slightly deeper at 13 than it was at age 12, as a result of his voice actor aging.

In an interview in early 2012 (at the end of season three), Pen Ward stated that Finn was now 14.

Possibly as of "Earth & Water," he is now 15, assuming he is the exact same age as Flame Princess, current age.

In "The Comet," Finn is now 16 years old.

Trivia

 * In the pilot, Finn is voiced by Zack Shada. However, in the series, he is voiced by Zack's younger brother, Jeremy Shada.
 * Jeremy Shada can make Finn's voice crack when asked during episode recording to better represent his youth and growth.
 * In "Ocean of Fear," Finn is revealed to be thalassophobic, meaning fearing oceans or seas. Finn has no problem swimming in "Business Time," "My Two Favorite People" and "The Witch's Garden", however, because his fear is specific to the ocean, not small bodies of fresh water.
 * In "Marceline's Closet," Finn is shown to be terrified of spiders.
 * Finn technically is still the King of the Goblins; the goblins believe his scapegoat, Whisper Dan, to be him.
 * Finn has a fictional female counterpart: Fionna.
 * One of Finn's catch-phrases is being "all about" something. In "Freak City," Finn says he is "frickin' all about sugar". Yet, he also explains that he is even more "all about feeding hobos." In "The Real You", Finn shouts "I'm all about stupid!"
 * In "Dad's Dungeon," it's revealed that Finn cries rarely; only in such devastating situations, as death or being repeatedly rejected by his love, Princess Bubblegum, does he cry.
 * Finn is very tolerant of pain. When the deer from "No One Can Hear You" breaks Finn's legs twice Finn whispers, "Whatever."
 * Finn and Jake frequently use math terms as catch-phrases (e.g., mathematical, rhombus, algebraic).
 * Finn's favorite color is baby blue "boy style," as revealed in "The Silent King".
 * When Finn is wearing his doctor suit in "His Hero," he has three Scientific Parasites in his pockets.
 * Finn's favorite food is meatloaf, as stated in "Still".
 * In "Jake vs. Me-Mow," Finn carries his adoptive mother's music box in his pack and knows her lullaby by heart.
 * Finn seems to speak Latin (as evidenced in "Morituri Te Salutamus"), although this may be caused by the magical powers of Fight King's arena.
 * In "Daddy's Little Monster," for the first time he becomes an antagonist by wearing the Nightosphere amulet, although it is only temporary.
 * Finn has coulrophobia, or fear of clowns, as shown in "Another Way".
 * Stormo is a creation partially made from Finn's DNA from the episode "Goliad."
 * Finn can defeat The Lich without using his pink sweater or without the jewelry and without the gauntlet because he realized that the ultimate weapon against The Lich is the power of "liking someone a lot."
 * Finn McCool was an adventurer and hero of Irish mythology. "Finn" is actually a nickname meaning "blonde".
 * Finn loss his right arm the same as Naruto Uzumaki from Naruto Anime.
 * His right robotics right arm same as Edward Elric from Fullmetal Alchemist.

References in other media

 * Finn and Jake appeared twice on the series MAD.
 * Finn appears as a playable character on Cartoon Network's TKO where his special moves are Look Out Below (when Jake falls on your opponent) and Sidekick Swing (when Finn grabs Jake's paw and Jake swings him at the opponent) and his super move is when Jake falls onto the opponent with an axe.
 * Finn and Jake were voted best duo of 2010, surpassing Regular Show's Mordecai and Rigby.
 * Finn and Jake appeared on the series Futurama (episode name: Leela and the Genestalk).
 * Finn, Jake, Bubblegum, Lady Rainicorn, Ice King, Stanley the watermelon, and the Reaper are characters in the game FusionFall, in which the player helps Finn save two princesses, get shirts from Stanley, and train with Finn in the petting zoo (Generator Rex).
 * Like most of the main characters, Finn is an Exosuit in the game Project Exonaut.
 * In Legends of Ooo, it is seen that Finn has a telescope which he uses to spy on Princess Bubblegum.
 * He has several games on the Cartoon Network website.