Frisk

Frisk is the playable character and main protagonist of Undertale. After Frisk falls into the Underground, they embark on a journey to return to the surface. Frisk is the last of the eight humans to fall into the Underground after traveling to Mt. Ebott. Frisk is not the "fallen human" named at the beginning of the game.

Appearance
Frisk is a human child who wears a striped purple and blue shirt, blue pants, and brown shoes. They have medium length straight brown hair, short bangs, and a blank expression. Though stoic in the overworld, NPCs often describe Frisk's expressions.

Personality
Frisk's name is revealed in only the True Pacifist Route. The player can project their personality onto Frisk because much about them remains ambiguous. Frisk speaks to NPCs throughout the game, but the exact dialogue is not shown. NPCs dialogue boxes display "..." to show that the NPC is listening to Frisk, and some NPCs respond to questions that Frisk asks.

Depending on their actions, players can interpret Frisk as merciful or merciless. Some NPCs emphasize Frisk's kindness, understanding, and grace in the epilogue. Frisk is obedient and only disallows player input when they follow someone else's instructions, such as when Sans tells them to hide behind the conveniently-shaped lamp.

Abilities
Frisk's determination grants the unequaled power to SAVE and heal at SAVE points. The SAVE file can be reloaded to repeat events that occur after it, but NPCs memories are not completely erased unless a True Reset occurs. This power emerged when Frisk first awoke in the Ruins.

Neutral Route
Flowey attempts to kill Frisk after he pretends to offer honest advice. Toriel intervenes, fireballs Flowey, and serves as a guide of the Ruins. At the end of a long room, Toriel asks Frisk to wait for her to return and states that she has errands to do. To be safe, Toriel gives Frisk a cell phone to call her with.

Frisk travels through the remaining puzzles in the Ruins and eventually arrives at Toriel's home. They ask Toriel "how to exit the RUINS," which prompts Toriel to destroy the Ruins's exit. Toriel then battles Frisk because she wants them to prove that they can survive outside of the Ruins.

Then, Frisk meets Sans and Papyrus in Snowdin Forest. The brothers set up traps and puzzles in an attempt to capture Frisk. After passing through Snowdin, Papyrus battles Frisk.

Undyne, the head of the Royal Guard, pursues Frisk throughout Waterfall. Monster Kid often saves Frisk from Undyne on accident because they are so excited to see Undyne in action. After a chase scene, Undyne destroys a bridge that Frisk is standing on, and Frisk falls into the garbage dump. Before they stand up, they recall a memory from the first human. In the garbage dump, Mad Dummy battles Frisk because Frisk mistreated their cousin, Dummy, in the Ruins. At the end of Waterfall, Undyne battles Frisk after she gives an abridged monologue atop a crag.

After entering Hotland, Frisk enters a lab and meets Alphys and Mettaton. Alphys tells Frisk that she is not a bad guy, and Mettaton interrupts them with a quiz show. Alphys gives Frisk an upgraded cell phone after the quiz show concludes, and she says that she will guide Frisk through Hotland and the CORE. Before his battle at the end of the CORE, Mettaton reveals that Alphys had created all of the traps in Hotland in an attempt to endear herself to Frisk. He then transforms into Mettaton EX and battles Frisk.

While passing through New Home, the capital of the Underground, Frisk learns the story of Asgore and Toriel's children from passing monsters. Then, Sans judges Frisk in the final corridor and explains the meaning of LOVE and EXP. He also emphasizes Frisk's importance in the fate of the world.

Escape
Frisk enters the Throne Room and finds Asgore. Asgore tries to make small talk, only to realize their fated confrontation. The two walk to the Barrier and Asgore gives Frisk one last opportunity to leave before fighting. Just before the fight, Asgore shows the six collected human SOULs, preparing the containment process after the battle. Right before the fight starts, Asgore destroys the MERCY button, making it impossible to spare or flee. However, at the fight's conclusion, Frisk can explicitly choose whether to spare or kill Asgore. Regardless of the choice made, Flowey will appear, destroy Asgore's SOUL, and take the human SOULs. The game then abruptly closes.

After reopening the game, Frisk finds that Flowey has saved his own game over the SAVE file, having gained the power to do so with the stolen human SOULs. Loading Flowey's game, Frisk confronts a powered up Flowey and defiantly steps forward, entering an initially hopeless battle with him. After Frisk calls for help several times, the stolen SOULs begin to revolt: first, they heal Frisk, and then they weaken Flowey, leaving him vulnerable to destruction. After reducing his HP to 0 and listening to his monologue, the SOULs remove Flowey's ability to SAVE or LOAD. After this, the SOULs leave Frisk and Flowey alone. At this point, there is an option to kill or spare a weakened Flowey before leaving the Underground, return to the surface, and end their journey.

After leaving the Underground, Frisk receives a call from Sans, who leaves a message about what happened to the Underground after Asgore died. This varies based on what monsters were killed and what friendships were completed.

True Pacifist Route
To complete the True Pacifist Route, Frisk must have first completed the Neutral Route.

If Frisk has completed the Neutral Route without gaining any EXP or LV (i.e. without killing anyone), it is possible to backtrack in the existing SAVE file to complete any missing friendships, then achieve the True Pacifist ending.

If Frisk acquires any EXP or LV, they will have to reset the game to achieve the True Pacifist Ending.

Friendships
While Frisk befriends many of the monsters in the Underground, only the Undyne, Papyrus, and Alphys friendships are necessary to achieve the True Pacifist Ending.

Frisk gains Toriel's friendship by sparing her, but she does not make another appearance until the end of the route.

Frisk gains Sans's friendship by sparing Papyrus, and can optionally hang out with him twice (once at Grillby's, once at the MTT Resort,)

Frisk gains Papyrus's friendship by visiting him at his home and hanging out or dating him.

Napstablook can be befriended by smiling at them in the Ruins, and hanging out with them at their house.

If Frisk chooses to give Undyne some water after being pursued, Undyne can be befriended. Otherwise, a reset is needed to achieve Undyne's trust and friendship. Frisk visits Undyne with Papyrus's help, and Undyne gets "revenge" by trying to befriend Frisk and become besties, setting her house on fire in the process. She tries to fight Frisk to regain honor but realizes that Frisk is a "wimpy loser with a big heart" just like Asgore and decides to be friends.

Mettaton can be befriended by sparing him; survive enough turns without killing him.

Undyne, having been encouraged to send a love letter to Alphys, gives the letter to Frisk, who delivers it to Alphys. This results in a date sequence with Alphys in which she and Undyne realize their feelings for each other and Alphys begins to come to terms with her past mistakes.

After befriending Alphys, Papyrus will recommend traveling to Alphys's lab. In the lab, there is a letter on the floor that, when picked up, reads a monologue and the instructions needed to proceed to learn "the truth." Walking through the bathroom door reveals an elevator which goes down to the True Lab after a malfunction. Frisk proceeds to explore the True Lab and along the way learns of Alphys's failed experiments (amalgamates) with determination and also about the origin of Flowey. After exploring the True Lab and talking to Alphys, she gains the confidence to reveal the truth about her experiments to the rest of the Underground. While attempting to leave, Frisk receives a phone call in the elevator from an unknown voice. The elevator immediately and forcibly brings Frisk to New Home.

Barrier
After returning to the throne room and confronting Asgore again, the pre-fight dialogue is interrupted by Toriel, who stops Asgore from fighting Frisk. Toriel is immediately followed by the other main characters who encourage everyone to get along. However, in a surprise twist, Papyrus reveals that it was actually "a little flower" who told him to bring everyone there. Immediately after this reveal, Flowey appears, having stolen the SOULs of the six other humans. He attempts to kill Frisk, but Undyne, Toriel, Alphys, and Papyrus use their power to block Flowey's finishing blows. Directly after this, all of the Underground's monsters arrive to encourage Frisk in the fight against Flowey. However, Flowey reveals that this has what he wanted all along so that he could absorb the souls of all the monsters in the Underground along with the six human SOULs.

Due to the immense power gained from the six human SOULs and all of the monster SOULs, Flowey can transform into his true form, and just before the fight begins it is revealed that he is actually Asriel Dreemurr. During this fight, Frisk is invincible, and any hit that would normally result in death will instead cause the heart to split, but reform back together. The first time this happens, it is accompanied by the text "but it refused." After stalling for long enough, Asriel transforms again. At this point, Frisk can feel the souls of Toriel, Asgore, Alphys, Undyne, Papyrus, and Sans within Asriel and the ACT button changes to SAVE to represent the act of freeing everyone's souls. This is accomplished by completing a short sequence of ACT options to restore the memory of each lost soul after selecting the said lost soul of a chosen character. After saving each monster, Frisk realizes that there is still one more person to save. After choosing to save "someone else," Asriel's memories of the first human (who strongly resembled Frisk) begin to play in a slideshow style. It is then revealed this "someone else" is Asriel himself. After this, Asriel starts to feel the love the monsters feel for Frisk through the souls he has absorbed, and slowly loses the will to fight as he is overcome with his fear of dying alone.

After reverting to his child form, Asriel learns Frisk's name. He apologizes for hurting everybody, and Frisk can choose to forgive or not forgive Asriel. Regardless of the choice made, Asriel destroys the barrier using the power of all of the SOULs before releasing them. Knowing that he will turn back to a flower without the power of the SOULs to sustain him, Asriel says one last goodbye to Frisk before leaving. At this point, there is a choice to hug Asriel or do nothing.

Freedom
After the scene with Asriel finishes, Frisk wakes up in front of Toriel, Sans, Papyrus, Undyne, Alphys and Asgore. While the monsters remember little about Flowey and nothing about his incarnation as Asriel, they do know Frisk's name. At this point, Frisk can backtrack through the Underground and talk to the other monsters, before returning the surface.

Backtracking to the very first room in Undertale reveals that Asriel is tending to the flowers. Asriel will ask about Frisk's desire to travel up Mt. Ebott in the first place. Receiving no answer, Asriel lists off foolishness or fate as possible motives, but comes to the conclusion that "only you (Frisk) know the answer." The actual reason is never revealed.

After passing through the final door to the surface, Frisk leaves the Underground with friends. Asgore offers Frisk the chance to be the monsters' ambassador to the humans. Most of the main monster cast then leave, except for Toriel, who asks about Frisk's plans. At this point, Frisk can choose to stay with Toriel or to go elsewhere.

After choosing to stay with Toriel, the ending scene shows Toriel bringing a slice of pie to Frisk's bedroom. Otherwise, if Frisk has "places to go," the game ends with a group photo of the main monster cast with Frisk in the middle.

Name
To "Frisk" means to skip or leap playfully, or to pat down on someone, looking for a hidden item. "Frisk" is the Swedish and Norwegian word for "healthy," and the Danish word for "fresh." "Frisky" means "playful and full of energy."

Naming the fallen human "Frisk" will initiate Hard Mode.

Trivia

 * In a joke thread on Starmen.net, Toby Fox posted early files from Undertale saying they were from an EarthBound hack called "UnderBound 2."
 * It was said that Frisk was a young androgynous child who was the step-cousin of "Squeezo" from the non-existent EarthBound hack, "UnderBound."
 * Frisk was also shown to have black outlines with darker hair and shoes compared to the lighter brown seen in the final version of the game.
 * It was also mentioned that Frisk's love interest was a female Cuban cigar.
 * Frisk and Flowey are the only two with the ability to SAVE, LOAD, and reset their SAVE FILE.
 * It is also implied that the first human's SOUL also had a great deal of determination since their SOUL is red, similar to Frisk's.
 * While Frisk is allergic to Temmie, this is not true of the other furry residents of the Underground.
 * Frisk appears to be left-handed. Evidence includes:
 * Holding the umbrella and glass of water using their left hand.
 * Offering their left hand to Toriel when she guides them through the Ruins.
 * The slicing attack animation curving to the right, implying that force was carried from the left to the right during the attack.
 * Most fatality battle sprites display steep slashes from top left to bottom right, a pattern difficult for someone who is right-handed.
 * Out of all the humans that fell to the Underground, Frisk is the only human to survive the adventure.