Fluttershy

Fluttershy is the second major character the protagonist encounters in Colleentale. She saves the protagonist from Leslie and guides her through the Ruins.

Appearance
Fluttershy is a Boss Monster whose appearance resembles her human self from My Little Pony Equestria Girls. She has long eyelashes, and her irises are moderate opal. She wears a long purple robe that displays the Delta Rune on her chest. Fluttershy is seen with her reading glasses, one instance being in her house when reading a book on lion facts.

Personality
Fluttershy is a kind monster that acts as a protective mother for the protagonist. She employs tough love on the protagonist as well as Asgore Dreemurr. She cares for children and was excited to become a mother.

She enjoys cooking and bakes butterscotch-cinnamon pie as well as her favorite, lion pie.

Fluttershy has a playful side and loves puns and bad jokes and she even keeps a journal of puns.

Fluttershy is said to be intelligent and dreams of becoming a teacher. She has already prepared a curriculum for the protagonist by the time they reach her home in the Ruins. In the True Pacifist Ending Credits, she stands outside a school and, in the Family Ending of a Neutral Route, she starts her own.

Main Story
Before the events of Colleentale, she was married to King Asgore and had a son, Shadow the Hedgehog. When the first human fell into the Underground, she adopted her as their child. The deaths of their two children pushed Asgore to declare war on humanity, and as a result, she left him and retreated to the Ruins.

Between then and the time the protagonist enters the Underground, she had seen Asgore murder multiple humans and reap their SOULs.

Neutral Route
At the beginning of the movie, Toriel saves the protagonist from Leslie, healing any damage done by the murderous daisy. After introducing herself, she guides her through the first few rooms of the Ruins. She encourages the protagonist to deal with monster encounters by talking to them, as opposed to acting violently.

She gives the protagonist a cell phone to keep in contact with one another, as she needs to run some errands further into the Ruins. She tells her to stay where she is, only to be disobeyed. She calls the protagonist frequently as the protagonist goes through the Ruins, and is about to call her again when she finds the protagonist at the entrance to her home.

She introduces the protagonist to her room and plans to raise her as her own. After the protagonist asks her about leaving the Ruins, Toriel abruptly leaves; the protagonist follows.

As she goes toward the exit of the Ruins, she explains that she plans to destroy the exit to prevent the protagonist from leaving, as all other humans who left had died.

At the end of the Ruins, Fluttershy tells the protagonist to prove that she is strong enough to survive and fights her in a test of strength. She can be killed or spared; if spared, Fluttershy lets the protagonist go but tells her not to come back.

Dragonizer the Dragon tells the protagonist during her rendezvous, that he and Fluttershy have been friends for a while, bonding over their love of jokes and puns. Neither of them knows each other's name or face, as they communicate through the door that blocks off the Ruins.

Dragon also says that Fluttershy asked him to protect any human that left the Ruins. He remarks that if not for that promise, the protagonist would be "dead where [she] stand."

True Pacifist Route
Fluttershy reappears just as Asgore and the protagonist prepare to fight, interrupting it with her kindness magic, much like she does with Leslie at the start of the movie. She explains the motive of her arrival was the realization that the protagonist would have to take a life to leave and that she had been trying to prevent such a thing from the beginning.

As the protagonist's friends come, she introduces herself to them and recognizes Dragon's voice immediately. She tells the protagonist that while she may have to stay Underground with all her friends, she will live a happy life regardless.

Leslie then appears. Having absorbed the human SOULs, he binds Fluttershy and company with vines. When Leslie tries to kill the protagonist, Fluttershy is the first monster to intervene, using her kindness magic to block Leslie's bullets. Her SOUL, along with every other monsters', is eventually absorbed by Leslie, allowing him to become Shadow.

During the protagonist's battle with Shadow, Fluttershy appears as one of the Lost Souls.

Epilogue
After the fight against Shadow concludes, she learns the protagonist's name, "Colleen." She tells her that she is free to go through the Underground to talk to more of her friends. Meanwhile, Penny Fitzgerald upgrades Fluttershy's phone, allowing her to send text messages.

Colleen leaves the Underground with Fluttershy and her other friends. As the others leave Colleen to begin her life on the Surface, Fluttershy asks Colleen what she will do now. In the credits sequence, Fluttershy welcomes Miles "Tails" Prower to a school that she opened and teaches at. The school door is adorned with the Delta Rune without the triangles that represented the monsters trapped Underground.
 * If Colleen decides to stay with Fluttershy, she says that none of this would have happened if she remained with her at the beginning of the movie and that it was for the best that she decided to leave the Ruins. She then promises to take care of Frisk for as long as she needs. Like in the Ruins, Fluttershy takes Colleen's hand as they walk offscreen together. After the credits, Fluttershy brings a slice of pie to Colleen's room.
 * If Colleen says that she "has places to go," Fluttershy says that she will see her later. After the credits, Colleen and her monster friends are shown together in a sepia photograph.

The Protagonist
Fluttershy cares for humans who fall into the Ruins and the protagonist is no exception. She tries to keep the protagonist in the Ruins, as Asgore killed the other humans who left her care. If the protagonist spares her, she lets her leave the Ruins, but not before giving her a parting hug.

If the protagonist kills her during a Neutral Route, she uses the last of her strength to give her a warning about what lies ahead and calls the protagonist "my child" before she turns to dust. If the protagonist kills her when she offers mercy, she says that the protagonist is like the monsters outside the Ruins. In the Genocide Route, she realizes that the protagonist is dangerous and laughs hysterically before she dies. The death design for Toriel is the same in a Genocide Route and on a Neutral Route if the protagonist kills her after she is spared thirteen times.

If the protagonist calls Fluttershy "mom," it surprises her, and she states that if it makes her happy, then she heartily approves of it.

Calling Fluttershy on her phone in the Ruins and flirting with her makes her assume the protagonist is joking, if she does it again she is unsure what to make of it. If she flirts with her after calling her "mother," she becomes uncomfortable and calls the protagonist an "interesting" child. She also mentions this in the epilogue.

If the movie is reset, Fluttershy says that talking to the protagonist is like "meeting an old friend for the first time" and also says that she feels this way about most fallen humans.

Asgore Dreemurr
Asgore is Fluttershy's ex-pet. They were once extremely close, winning first place in the '98 Nose Nuzzle competition and were open about their affection for one another. During their marriage, Fluttershy's nicknames for Asgore included "Fairybuns" and "Gorey."

Fluttershy left Asgore and New Home after he declared war on humanity. After they are reunited on a True Pacifist Route, Fluttershy criticizes his plan for freeing monsters but still believes that he deserves mercy, even though he is "terrible." When Asgore asks if they can be reconciled or at least be friends, Fluttershy declines. While she appears to be civil with Asgore when she speaks to him about the future of the Underground in the aftermath of the fight against Shadow, once they are on the surface and everyone else has left, Asgore wonders whether he should leave too, and Fluttershy glares at him, prompting him to leave her and Colleen alone. However, in the ending credits, she does not mind his presence while trimming the bushes, hinting a developing tolerance or gradual forgiveness.

Leslie
Fluttershy calls Leslie a "miserable creature" as she kindly attacks him to protect the protagonist. She is unaware that Leslie is Shadow.

Dragonizer the Dragon
Dragon and Fluttershy do not meet in person until the end of a True Pacifist Route and the Family and Exiled Queen endings, where they both have become good friends. They started their friendship by telling jokes to each other through the door leading to the Ruins. One day, Fluttershy entrusted Sans with protecting any human that left the Ruins.

They continue to bond in the epilogue and text each other as Colleen backtracks through the Underground.

Trivia

 * Like some other characters, Fluttershy kept the same role.