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.

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.

Frisk
Despite wanting to capture you, Papyrus still cares about you, and eventually ends up dating/hanging-out-with 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.

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.

Sans
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. Sans also takes Papyrus to heart and would give you the nickname of a "Dirty Brother Killer" if you killed him, and in a Genocide run, asks Papyrus himself, whom is already long dead, if he wants anything from Grillby's shortly before Sans' death.

Undyne
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.

Flowey
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.

Trivia

 * He is named after the font he speaks in, Papyrus, just like his brother, Sans.
 * 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.)
 * Papyrus and Sans were inspired by the webcomic Helvetica, which features a skeleton named after a font.
 * Note the design on Papyrus' shirt heavily resembles the logo of Starman from the Mother series.
 * If you type "Papyru" for the character's name, the response becomes "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).
 * 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.