Underswap:

Underswap swaps characters in a pair

Ex (alphys and undyne)

Storyshift:

Swaps a pair of characters with another pair of characters that have something in common they do not exchange roles

Ex (alphys and undyne as napstablook and mettaton but these two are Asriel and chara)

Swapswap:

Swapswap swaps swapped characters in a pair

Altertale:

Soriel that’s it

Ex (undyne and alphys stay the same)

Storyspin:

They take the role of the character that had their role in Storyshift

Ex (undyne and alphys are toriel and asgore)

Otherswap:

Same thing as in underswap but the other pairings

Ex (undyne and alphys swap with papyrus and sans)

Swapswapswap:

Swapswapswap swaps swapped swap characters in a pair

A different swap:

Same thing as in otherswap but the different pairings

Ex (undyne and alphys swap with burger pants and dess)

Shopswap

Shopkeepers swap with the main cast

Ex (undyne and alphys swap with gerson and temmie)

a tale between the stars

It’s like underswap but the stars chose the roles

Ex (undyne and alphys swap with papyrus and sans)

Twisted will

It’s like Storyshift kinda not really but they twisted the roles until it turned purple

Ex (undyne and alphys are papyrus and sans )

Flipflopped

The roles flipped and flopped all over the place

Ex (undyne and alphys are papyrus and sans)

convertedtale

Minor characters swap with major characters

Ex (undyne and alphys swap with whimsun and temmie)