Papyrus/History

Pre-SHAETALE (Pre-Shae)
Papyrus lived with his family in the Capitol until his father, Gaster, fell into the CORE and Ariel, his mother, disappeared when he was still very young, leaving him to be raised by his older brother Sans. The two soon moved to live in Snowdin, where Papyrus ended up growing up and staying in until Shae freed monsters years later in his early adulthood.

Pre-SHAETALE (Post-Shae)
The 8th human to fall into the underground, Shae, reunites the brothers with their father W.D. Gaster. Shae is adopted at some point and stays in the skelebros' house.

Beginning Arc (Christmas Arc/Prank Sub-Arc)
Papyrus participates in the prank war the family wages on itself, siding with his siblings to prank Gaster. Papyrus eventually meets his long-lost mother Ariel, who was revealed to be the riverperson. He convinces her to come stay at the skelebros' house for Gyftmas (Christmas), and helps with convincing her to reunite with the family for good. After Gyftmas (Christmas), Papyrus begins to date Mettaton, who he had a mutual crush on. Papyrus also comes out as gay around this point, and is happily accepted by his family.

Jerry's Debut
With Jerry's powers, Papyrus is rendered completely blind. His vision goes back to normal after the arc ends. He has a nightmare of Sans throwing him into the workshop, foreshadowing BB's debut weeks later. After Shae being rescued from drowning, Gaster yells at him out of stress, causing a minor fallout, which Papyrus goes off sadly to Undyne's to train.