Alphys

Dr. Alphys (/ˈælfiːz, -fᵻs/ AL-feez, AL-fis) is a female, reptilian monster that lives in the lab in western Hotland. She is the incumbent Royal Scientist, a position she was awarded by Asgore after the death of her predecessor. Asgore hired Alphys because she told him that she had created a SOUL; in reality, she created a robotic body for a ghost.

Appearance
Alphys is a yellow, reptilian monster of similar height to the protagonist. She has scales, round glasses, protruding teeth (which seem to vary between two and three depending which way she faces), and normally wears a white lab coat. However, she wears a black and white polka dot dress on her date with the protagonist.

Personality
Alphys is a nerdy, shy recluse with a fondness for human anime and manga. She has crush on multiple characters (some mild, others more serious ), but struggles to communicate her feelings.

Alphys is filled with guilt and insecurities about herself and her accomplishments. After she accidentally created the Amalgamates while experimenting with determination, she told nobody and became depressed.

Main Story
Before the events of Undertale, Undyne met Alphys in the Garbage Dump, where Alphys was deep in thought. Alphys accidentally created the Amalgamates through experiments with determination sometime before the protagonist falls into the Underground.

Neutral Route
Alphys initially meets the protagonist in her lab. She explains that she has watched the protagonist throughout their journey using hidden cameras and adds that she wants to help guide the protagonist through Hotland.

Alphys explains that a robot she created, Mettaton, wants to kill the protagonist. Mettaton then bursts the wall and forces the protagonist into a quiz show; Alphys helps the protagonist by signing the letter of the correct answer with her hands. Mettaton catches on after Alphys excitedly answers a question about her favorite video game, and Mettaton embarrasses Alphys by asking the protagonist who they think Alphys has a crush on.

After Mettaton's quiz finishes and he flies away, Alphys offers her phone number to the protagonist. She notices that their cell phone is old and quickly upgrades it with features including texting, a key chain, links to two dimensional boxes, and access to the UnderNet. Alphys explains these upgrades and rushes into her lab's "bathroom."

As the protagonist progresses through Hotland, Alphys frequently updates her UnderNet status. She calls to help the protagonist with puzzles but dislikes to give them the solutions outright. Alphys stops posting status updates when she realizes that the protagonist has been reading them the whole time.

Mettaton antagonizes the protagonist in several deathtraps, but Alphys informs the protagonist of a phone upgrade to aid them in every situation. If the protagonist fails any of Mettaton's challenges, Alphys blames herself, and Mettaton helps her out by letting the protagonist go. Alternatively, Alphys takes some credit if the protagonist succeeds.

Alphys attempts to guide the protagonist through the CORE but struggles doing so because of the CORE's ever-changing layout. If the protagonist follows her instructions, they often encounter hostile monsters. If the protagonist does not follow her directions, she worries about their trust in her.

At the end of the CORE, Mettaton reveals that Alphys inserted herself into the protagonist's journey by creating obstacles for them to overcome together. While she is locked outside, Alphys instructs the protagonist to turn Mettaton around and flip his switch, making him vulnerable. After the fight, Alphys unlocks the door and looks at Mettaton's body. If the protagonist spared Mettaton, Alphys is relieved that he just ran out of battery power. If the protagonist killed Mettaton, Alphys pauses and slowly reassures them not to worry. She stays with Mettaton's body as the protagonist progresses into the next room.

Alphys catches up with the protagonist before they take the elevator to New Home. She admits that she lied to the protagonist, and that the protagonist will have to kill Asgore to pass through the barrier. She then leaves.

True Pacifist Route
After the protagonist delivers Undyne's Letter to Alphys, Alphys reluctantly goes on a date with the protagonist because she thinks that they wrote the letter. She changes into a dress and takes the protagonist to the Garbage Dump for their date.

While there, the protagonist and Alphys roleplay to help Alphys open up to Undyne about her feelings. Undyne overhears them talking about her and approaches. Alphys confesses that she was trying to impress Undyne by making her hobbies sound more scientific, and Papyrus takes Alphys out for a lesson in self-confidence. Their training ends early and he sends her home.

True Lab
When the protagonist returns to the lab, a note from Alphys lays on the ground in front of the "bathroom." The note directs the protagonist to the True Lab's entrance to discover the truth, in case they do not hear from her again.

The protagonist learns about Alphys's determination experiments in the True Lab via consoles on the walls that have her lab entries on them. She isolated determination from the six human SOULs and injected it into monsters who had "fallen down" in an attempt to extend the longevity of their SOULs after death. None of the monsters died, and they were well for a short time before they melted together.

Alphys's lab entries explain that monsters lack the physicality that humans have, and that this is why the monsters fused together; their bodies could not handle high concentrations of determination. She did not tell anyone about the Amalgamates and feared hurting everyone's feelings.

As the protagonist reaches the power generator, Amalgamates approach and trap them. Alphys stops the Amalgamates and explains that they were "sassy" because they were hungry. Alphys then tells the protagonist that she had a change of heart and will tell everyone about her failed experimentation.

She then leaves the lab and returns the Amalgamates to their families.

Alphys also joins Undyne in breaking up the fight between Asgore and the protagonist. Alphys is surprised to see two boss monsters, and comforts Asgore after Toriel rejects his bid of friendship. Mettaton prompts the two to kiss, but Toriel interrupts them from doing so.

Alphys questions how Papyrus knew to call everyone to New Home, and appears alarmed when Papyrus informs her that " A TINY FLOWER HELPED ME. "

After Flowey ensnares the protagonist's friends, Alphys encourages the protagonist by stating her faith in them. Flowey absorbs her SOUL along with the SOUL of every monster in the Underground.

Alphys appears as a Lost Soul during Asriel Dreemurr's battle.

Epilogue
After Alphys regains consciousness, she remembers little about what happened. She tells Asgore and Toriel about her failed experimentation; Toriel fires her.

After the protagonist wakes up, she discusses her plans to watch anime when they leave for the Surface. She also helps explain what anime is to Asgore, and asks for Frisk's help in doing so. Alphys tries to show Asgore anime on her phone but accidentally shows him a picture of robots kissing.

On the Surface, Alphys joins Undyne, who leaves to check on Papyrus. In the True Pacifist Ending Credits, Alphys relaxes on the beach with Undyne, Lesser Dog, Greater Dog, the Nice Cream Guy, and Onionsan. Undyne kisses her on the cheek, and she faints.

Genocide Route
After Undyne calls her, Alphys evacuates monsters in Hotland to the True Lab. However, a few monsters remain including Muffet and Burgerpants. She does not confront the protagonist directly.

Mettaton
Before the events of Undertale, Mettaton (as a ghost) started a Human Fanclub. The only person who joined was Alphys, who showed Mettaton designs of a robot she wanted to build for him.

Alphys worries that Mettaton will leave her behind after she finishes his body. She cares deeply about Mettaton, and would not know what to do if he was gone.

Alphys disappears in Neutral Route endings where the protagonist killed either Mettaton or Undyne; it is hinted that she may have committed suicide.

Undyne
Alphys has a crush on Undyne, but Alphys fears Undyne finding out the truth if she confesses her feelings. Alphys tries to impress Undyne because she does not want Undyne to think that she is a nerdy loser. She also names variables after Undyne, writes her name in the margins of her notes, and writes fictions about them sharing a domestic life.

Alphys shares her love of human anime and manga with Undyne, though Alphys convinces Undyne that anime and manga are actual depictions of human history.

Together, they hang out at Alphys's lab, where Alphys makes "chilly pink stuff" for Undyne. Alphys also helped Undyne create some of Waterfall's puzzles.

On a True Pacifist Route, Alphys and Undyne begin dating, and, in the True Pacifist Ending Credits, Alphys faints after Undyne kisses her on the cheek.

The Protagonist
Alphys admires and supports the protagonist as they adventure through the Underground. She watches them via hidden cameras from the moment they leave the Ruins. She attempts to insert herself into the protagonist's journey by creating obstacles in Hotland, but she later admits that this was just an attempt to make herself feel better.

She dates the protagonist because she believes that the protagonist wrote Undyne's love letter; Alphys later admits that she has no interest in actually dating the protagonist and was only pretending to go on a date to be nice.

If the protagonist aborts a Genocide Route in Hotland, however, Alphys holds no positive feelings for the protagonist and says that she should have killed them when she had the chance.

Asgore
Alphys works for Asgore as the Royal Scientist. She lies to Asgore about creating a SOUL and presents Mettaton as proof of her achievement in an attempt to impress Asgore.

She tries to do what Asgore asks of her, which leads to the failure of the determination experiments.

Alphys has a crush on Asgore and sometimes refers to him as "Mr. Dreamy." In the epilogue, Alphys comments that she has moved on from Asgore, and adds that she thinks Asgore and Toriel are a cute couple.

Toriel
Alphys did not know about Toriel until Alphys met her while interrupting Asgore's fight with the protagonist. Even though Toriel fires her as Royal Scientist, Alphys easily befriends Toriel. Alphys also finds her attractive.

When Toriel questions how anyone could flirt with her, Alphys laughs hysterically. This is a likely reference to the positive fan reception of Toriel after the demo. Alphys also expresses her love of the "Tori and Gorey" ship, adding that she may write a lot of fanfiction about it.

Bratty and Catty
Alphys used to live on their street. She was like a big sister to them and took them on trips to the Garbage Dump to find cool junk. They reveal that Alphys made Mettaton to impress Asgore, and add that no one has seen Alphys recently.

Alphys evacuates Bratty and Catty on a Genocide Route.

Trivia

 * Alphys is an anagram of "shy pal"; this could be where her name came from.
 * It is also possible that Alphys's name was derived from the word "alpha," or the dominant leader of a group. This could allude to her role as the Royal Scientist.
 * There is one instance where Undyne uses the possessive case of Alphys, possibly using the nickname "Alphy."
 * When attempting to name the Fallen Human "Alphys," the response becomes "D-Don't do that." and prevents the name from being used. However, naming the fallen human "Alphy" gives a confused "....OK????" and is allowed.
 * Alphys may know Sans; dialogue in the epilogue hints at this.
 * Alphys's favorite anime, "Mew Mew: Kissy Cutie," may be a reference to Tokyo Mew Mew (also known as Mew Mew Power in North America), a typical romance magical girl anime.
 * Posters in Alphys's lab share design characteristics with Mew Mew Power.
 * Before the protagonist enters the True Lab, there is a note in the trash can that reads "I KNOW WHAT YOU DID." Flowey may have written this note to push Alphys to reveal her secrets.
 * Alphys is the only major monster in the game who the protagonist cannot fight and, therefore, kill.
 * Alphys's full combat capabilities are unknown. In the True Pacifist Route, she generates a wall of electricity to protect the protagonist's SOUL from Flowey's bullets. In the subsequent battle against Asriel Dreemurr, Alphys's Lost Soul uses some of Mettaton EX's attacks.
 * In the game's strings in the part where the answers to Mettaton's quiz of "who Dr. Alphys has a crush on," it says "LOOLLLL IF YOU CAME TO THIS PART OF THE CODE TO SEE WHO I HAVE A CRUSH ON YOURE OUT OF LUCK." This is a joke hidden in the game's code as Alphys's crush is clearly Undyne, and she is not mentioned in that section of the code.