Classics
The two most popular Undertale AUs
Underswap & Underfell
The protector of the multiverse
Ink Sans
The famous purple mix of two AUs
Swapfell
The murderous Sans
Dust Sans
Mettaton
The fanon name for Underswap Sans
Blueberry
The destructor of the multiverse
Error Sans
The double AU that goes back to Undertale
Swapswap
The Sans after Frisk leaves the underground
Horror Sans
The role of Sans in Storyspin
Chara
The cool Sans AU
Underfresh
The angel and dark angel of the multiverse
Dream and Nightmare
The three lazybones
Bad Time Trio
The Sans that teamed with Chara
Killer Sans
The "judge" in Shiftshift
Mettaton
The Sans AU that is just the theorized past of Sans
Science Sans
The most famous AU that talks about the multiverse
Underverse
The Megalovania name of many Sans bought together
Omnilovania
The trio of bad sanses
Murder Time Trio
Napstablook in Altertale
Trick question: Napstablook
A dirty, purple AU
Underlust
A sworded Sans, with a Chara inside of him
The AU that goes 90% back using whatever AU it's mixed with
Revert
The edgy one
The "judge" in Swapshift
Frisk