Skelebros

Fontcest is the slash ship between Sans and Papyrus from the Undertale fandom.

Variations

 * Skelebros - the familyship between Sans and Papyrus
 * Swapcest - the ship between the Underswap versions of Sans and Papyrus
 * Fellcest - the ship between the Underfell versions of Sans and Papyrus
 * Swapfellcest - the ship between the Swapfell versions of Sans and Papyrus
 * Edgeberry - the ship between Underfell Papyrus and Underswap Sans
 * BBQKetchup - the ship between Undertale Sans and Swapfell Papyrus
 * BBQTacos - the ship between Swapfell Papyrus and Underswap Sans
 * Papayaberry - the ship between Undertale Papyrus and Underswap Sans
 * Honeyketchup - the ship between Underswap Papyrus and Undertale Sans
 * HoneyMustard - the shop between Underfell Sans and Underswap Papyrus

Canon
Sans and Papyrus are brothers and are the fourth and fifth major characters you meet in Undertale. They have been shown to love each other more than seemingly anything, as they appear to have no other family.

Sans and Papyrus often compliment each other, while Papyrus still gets angry at Sans for being a "LAZYBONES!".

Fanon
Some people like to pair Sans and Papyrus, possibly because the shippers think they have sexual love for each other, despite it being brotherly love. Others hate the pairing due to it being incest.

Sometimes different AU versions (mainly Underfell, Underswap and Swapfell) of Sans and Papyrus are shipped. Some of the AU versions of Fontcest have unique names, with Classic Fontcest referring to the main versions.

Fandom
AO3

Tumblr

DeviantArt
 * fontcest tag on DeviantArt
 * papysans tag on DeviantArt
 * swapcest tag on DeviantArt
 * fellcest tag on DeviantArt
 * swapfellcest tag on DeviantArt
 * edgeberry tag on DeviantArt
 * papyaberry tag on DeviantArt
 * Fontcest fanclub on DeviantArt