Not all the character wll swap, so if you see some characters being the same is because that.

Also not finished yet:

Eve!Underswap Swaps:

Main Characters:

Frisk Doesn't swap

Flowey The Flower - Swaps With -> Flowey The Buttercup Flower

Asriel - Swaps With -> Chara

Chara - Swaps With -> Asriel

Toriel - Swaps With -> Asgore

Asgore - Swaps With -> Toriel

Papyrus - Swaps With -> Sans

Sans - Swaps With -> Papyrus

Undyne - Swaps With -> Alphys

Alphys - Swaps With -> Undyne

Napstablook - Swaps With -> Hapstablook (Mettaton)

Mettaton - Swaps With -> Napstabot (Napstablook)

Side Characters Swaps:

Grillby Doesn't swap

Burgerpants - Swaps With -> Muffet

Gerson Doesn't swap

Catty & Bratty Doesn't swap

Annoying Dog - Swaps With -> Temmie

Temmie - Swaps With -> Annoying Dog

Gaster Doesn't swap

River Person Doesn't swap

Mini Bosses Swaps:

Mad Dummy Doesn't swap

Royal Guard Dogs - Swaps With -> Royal Guard Cats

RG 01 & RG 02 - Swaps With -> RG 03 & RG 04

Muffet - Swaps With -> BurgerPants

Glyde - Swaps With -> So Sorry

So Sorry - Swaps With -> Glyde

Mad Mew Mew Doesn't swap

Places Swap:

Ruins - Swaps With -> New Home

Snowdin Forest - Swaps With -> Springly Forest

Snowdin Town - Swaps With -> Springly Town

Waterfall - Swaps With -> Hotland

Hotland - Swaps With -> Aquazone

Core - Swaps With -> Hydrotermic Reactor

New Home - Swaps With -> Ruined Home

Other swaps:

Photoshop desing concept - Swaps With -> Amalgam desing concept

Amalgam desing concept - Swaps With -> Photoshop desing concept