There are too many...

But I've decided to provide pictures and descriptions

 to my best abilities.

They will be in parts

due to the image limit.

Here we go...

Music: Undertale (Chime remix)

Aftertale- After the Genocide run, Sans stays in between realities with a different version of Frisk. He has a slash mark from where he was killed and one of this eyes is glitched and hidden.

Angeltale- Original Undertale characters are angels. 

Apocalypse- Original Undertale setting has changed to the apocalypse, where the characters try to help Frisk trough the wastelands.

BabyBones/LilSkelebros - Takes place when Sans and Papyrus were babies.

BananAsriel- Asriel stays in a banana costume.

Bromalgamate - When Papyrus was defeated in a Genocide run, Sans takes him to Alphys. She injects him with too much determination, which cause him to melt as Sans asks him what's wrong. He hugs him, holds him close, and tells him it's okay. This causes them to merge together, forming the Bromalgamate. 

Cattale - All original Undertale characters are cats, taken care of by Frisk. 

Comic Papyrus- A combination of Sans and Papyrus.

Dancetale- Original characters in Undertale love dancing. (And lemme just say, Sans looks fresh af XD)

Dogtale- Original Undertale characters are dogs. 

Dreemurr Reborn- Ariel Dreemuur is possessed by Frisk and brought back to life.

Errortale- Original Undertale characters, mainly Sans, live in between realities fixing glitches. They have the power of strings coming from their hands that can grab souls and other objects. Mainly intertwines with Underswap.