Undertale,
Underfell,
Underswap
Outertale
Swaptale
Bromalgamate
Disbelief
Possessed!Sans/Possessed!Papyrus
GasterBlaster!Sans/GasterBlaster!Papyrus
Dreemurr Reborn
Floweypot
Dogtale
Underworld
Alone Together
Gaster!Sans
Kindertale
Skelefrisk
Ageswap
Genocide!Grillby
Undermafia
Blind!Frisk
Limbotale
Core!Frisk
Undersail
Reapertale
Baby Bird
Omega Sans
Grouptale
Will add more.