Papyrus Gaster

Underground
Papyrus was created years after Sans, and while he was physically far more capable than Sans, his intellect didn't stack up. He's far more passive in nature than his brother or creator, who he referred to as his father during the time he knew him, but upon the CORE incident, Papyrus forgot of Gaster's existence just like everyone else save for Sans. He remained with his brother, often watching Undyne's training sessions through security cameras, growing an obsession with battling. When he and Sans moved to Snowdin, Papyrus decided to try and join the Royal Guard, doing everything he could to prove to Undyne his worth. She eventually allowed him, before trying to train him with other things, knowing he was too passive to be a real warrior. She kick-started Papyrus' culinary career. Many timelines happened after this, but the current one has Papyrus befriending Frisk, and allowing her to stay in his house whenever she pleases. When the CORE destablized, filling the underground with magma, the monsters fled the underground. The barrier was shattered by the combined efforts of Frisk, Flowey, and the six human SOULs.

The Surface
While on the surface, Papyrus shifted his attention from the disbanded Royal Guard to culinary skills, during which he befriended Mettaton, who offered Papyrus a spot on his show as the 'Skelechef'. Papyrus was an instant hit, so Mettaton kept him on through guest appearances as Papyrus' popularity grew. The two began to harbor feelings for one another, though they have yet to engage in a relationship. Mettaton endorsed Papyrus' brand of pasta known as 'Papasta', and also wrote the script for a new television show starring Papyrus in the lead role. Papyrus still finds time to spend with Sans, Toriel, and Frisk, though is often very busy acting with Mettaton.

Episode 1 "A Happy Ending"
Papyrus appears in Toriel's kitchen with Sans, giving a box of Papasta to Toriel before he eventually leaves. He doesn't appear again for the remainder of the episode, though he does send Sans a selfie intended for Frisk when Asgore brings her to Sans' house.