Why does the reader meet Underfell Sans because of a dog in the story?

Maybe the dog leads the reader to a mysterious place where they stumble upon Underfell Sans.

One great 'underfell sans x reader fanfiction' is 'A Dark Encounter'. It has a really interesting plot where the reader is thrown into the Underfell universe and has to navigate their relationship with Sans. The story is full of tension and character development.

First, understand the character of Underfell Sans. He's different from the normal Sans, more edgy and with a darker personality. Then, create an interesting scenario for the reader to interact with him. For example, a dangerous mission in the Underfell world.

The character development of Sans in this type of fanfiction is usually centered around his journey from a victim of abuse to a survivor. Initially, the abuse has left him with deep - seated insecurities and a negative view of the world. However, as he is exposed to positive influences, such as a caring friend or a new opportunity, his character begins to shift. He might start to develop new skills or interests that were suppressed due to the abuse. His relationships also change, from being guarded to more open and trusting. This development is often a slow and arduous process, but it is what makes the character so interesting in these fanfictions.

It's a combination of elements from different universes. The characters interact in unexpected ways, creating new and exciting storylines.

Frisk would be a likely candidate. Since Frisk is the main character in Undertale and has a very adaptable personality. They could approach Underfell Sans with an open mind and try to understand him.

Typically, in these fanfictions, Sans's character is shown with a great deal of internal struggle. He is constantly fighting against the effects of the abuse. He may be depicted as having mood swings, sometimes lashing out because of the pain he has endured. His relationships with other characters also become more strained due to the abuse, and he may have difficulty opening up or showing vulnerability.

The comic usually features darker and more sinister versions of Papyrus and Sans in a challenging and often dangerous world.

The comic likely explores their interactions and adventures in the Underfell universe, showing their unique personalities and challenges.

Underfell Sans comics usually feature a dystopian and chaotic world. The art style might be more edgy and the storylines more intense and challenging.