Papyrus

 Papyrus is one of the two skeleton brothers, the other being Sans, and a major character in the story. Befriending him is necessary to finish the True Pacifist Route. He wants to catch a human so that he can become a member of the Royal Guard.

Biography
Papyrus blocks the player's way out of Snowdin, but will not kill them. Eventually, he spares the player and lets them leave Snowdin. Flirting with him during battle will make him consider a date later. Otherwise, the player can still visit him at his skeleton home to hang out with him.

If the player goes on a skeleton date with Papyrus, he realizes that he doesn't like you in the same way he thinks you like him, and skeleton dumps you. He gives you his skeleton phone number so the two of you can still talk throughout the rest of the game.

On your way to Hotland, while walking past the 'Welcome to Hotland' sign, Papyrus calls you to tell you he thinks you and Undyne would make good friends. After this (assuming you spared Undyne and haven't killed any monsters), you can stop by Undyne's house to find Papyrus waiting for you. He tries to act as a skeleton wingman, and jumps out the window. Papyrus is still listening, however, which shows that he truly cares about you making friends with Undyne. If you manage to befriend her, when you call Papyrus afterwards at any point he will also allow her to talk on the phone as well.

At the end of the True Pacifist route, you learn that Papyrus had been either talking to or at least in contact with Flowey the entire game, and that said flower had alerted him to call everyone to the player at the ending. This is also confirmed by Sans at some point, who covers up his knowledge of Flowey with the assumption someone was pranking Papyrus with an echo flower.

Personality
Papyrus is a loud and flamboyant skeleton who presents a confident, charismatic image of himself. He tends to work hard, and despite his brash personality, he is a very kind skeleton at heart. Papyrus is occasionally rather oblivious and nonobservant, such as when he tries to rub different kinds of creams and "sauces" behind his ears, only to realize that he doesn't have any ears.

For all of his skeleton faults, Papyrus seems to match this with how overwhelmingly determined he is, a feature that made Undyne take notice of him when he waited from midnight to morning for her to accept him into 'royal guard training' even though the skeleton begged her.

He really likes spaghetti and cooks it in his spare time. Sans says that ever since he started taking lessons that his culinary talents have improved greatly. In a year, his food might even be "edible."

In Battle
All of his attacks are composed of bones moving across the screen, which start out easily avoided, but become much harder once he turns you blue. He also has a really cool special skeleton attack, as he tells you, but unfortunately he has to use a really neat looking normal attack because a dog stole it.

His "blue attack" turns you blue, which gives the element of gravity to the battle, and along with moving around to dodge attacks, you also have to jump.

If you lose against him, you will be captured, and placed within Papyrus's shed, from which you can easily escape. If you lose three times, you can bypass the battle entirely.

The Player
Despite wanting to capture you, Papyrus still cares about you, and eventually ends up dating you if you pick the pacifist route. He eventually, however, turns you down, as he realizes he does not feel the same way about you. He does genuinely care about you, though, as shown through keeping you out of danger, and worrying about your well-being when you escape his shed (if he captures you) because you didn't let him know that you were escaping. You remain friends throughout the game. If you pursue the Genocide route, in your battle with him, he instantly spares you and wishes to guide to on a better path and be friends. Even if you murder him in this route, he still believes that there is good in you and wants to be friends.

<font face="Papyrus" size="4.5">If you allow him to win in battle, he simply captures you and puts you in the shed, and asks you not to escape. Each time you escape (and allow him to win again) this escalates until Papyrus just gives you the option of not being captured at all.

<font face="Papyrus" size="4.5">Sans
<font face="Papyrus" size="4.5">Sans is Papyrus's brother, and though he often yells at Sans to stop being so lazy and he detests the many skeleton puns dropped throughout the game (especially Sans's), the two of them care about each other a lot. Sans refers to Papyrus as "cool". Papyrus often cleans up after Sans, and states that Sans is lucky to have such a cool guy taking care of him. He was also the one to convince Sans to get a job as a sentry.

<font face="Papyrus" size="4.5">Undyne
<font face="Papyrus" size="4.5">Papyrus and Undyne are good friends. Being the head of the Royal Guard, Undyne took Papyrus under her wing to train him, however instead of giving him fighting lessons, she gave him cooking lessons, because she believed he was too nice to join the royal guard. Still, Papyrus continues to try his best to capture a human so Undyne will let him join the royal guard. He believes that she and the player can truly get along, even offering to be their "wingman" for their friendship.

<font face="Papyrus" size="4.5">Flowey
<font face="Papyrus" size="4.5">In an optional conversation with Sans, it is implied that Papyrus has encountered Flowey, and that he receives flattery, advice, encouragement and predictions from Flowey, probably to Flowey's benefit. Flowey also told Papyrus to bring him and Undyne, Asgore, Sans, and Alphys, to bid the Player farewell. Flowey actually wanted them to gather in order to harvest their Souls and open the gate to the Surface.

<font face="Papyrus" size="4.5">Trivia

 * <font face="Papyrus" size="4.5">He is named after the font he speaks in, Papyrus.
 * <font face="Papyrus" size="4.5">This font/name may have also been chosen because the "Book of the Dead" was commonly written on a scroll of Papyrus paper. (the book usually depicted the dead and their journey into the afterlife.)
 * <font face="Papyrus" size="4.5">Papyrus and Sans were inspired by the webcomic Helvetica, which features a skeleton named after a font.
 * <font face="Papyrus" size="4.5">Note the design on Papyrus' shirt heavily resembles the logo of Starman from the Mother series.
 * <font face="Papyrus" size="4.5">If you type "Papyru" for the character's name, the response becomes "<font face="Papyrus">I'LL ALLOW IT!!! ". This makes Papyrus the only boss character who lets their name be chosen at the beginning of the game (if only because the character limit prevents you from typing out the full name).
 * <font face="Papyrus" size="4.5">His UnderNet username is COOLSKELETON95. Following the convention of using your birth year in your username, this puts him at 14 to 24 years old in the year 201X.
 * <font face="Papyrus" size="4.5">Toby Fox has confirmed that Papyrus' personality is slightly based off of the internet personality COOLSKELETON95.

<font face="Papyrus" size="4.5">Artwork
<font face="Papyrus" size="4.5">