Yes, there are many Sans x Tem fanfictions that focus on their friendship, adventures together, or other non - sexual relationships. For example, some might explore how they team up to face challenges in the Underground, or their daily interactions that are more about mutual understanding and support.
Writing fanfiction about incestuous or inappropriate relationships like that goes against the positive and family - friendly nature of the Undertale game. Such content is not acceptable in the general Undertale community, so I don't think there should be any available or promoted fanfiction of this sort.
Well, first of all, they are brothers. Incestuous relationships are considered unethical in most cultures and moral standards. In the context of Undertale, their relationship is one of brotherhood and friendship, not a sexual one. Fanfiction should enhance the positive aspects of the original work, not distort it with such inappropriate content.
Some characters might be amused. For example, Sans would probably make some witty remarks about the fanfiction's plot twists. Papyrus, on the other hand, might be a bit confused at first but then get really excited if he finds a heroic role for himself in the fanfiction.
Celebrating Years GIFs were a type of emoticon package and dynamic picture that received much attention in Celebrating Years. These animations could show the different emotions and personalities of the characters in the play, making people more interesting and cute when using them. Although the search results did not provide specific gifs for celebrating the New Year, one could use relevant software such as Waifu2x, Dain/Cain/Rife, Squirrel-Rife, etc. to fill in the gif frames and generate high-quality intermediate frames to create gifs for celebrating the New Year.
In a comical fanfiction, most of the characters would enjoy it to some extent. Sans and Papyrus would be great additions to a comical story, and they would probably laugh along with the funny parts. Frisk, depending on how they are portrayed in the fanfiction, would either be the source of the comedy or be reacting to the absurd situations. In a more serious and political - themed fanfiction about the Underground's society, Asgore and Toriel would have deep thoughts. They might discuss among themselves how the fanfiction's view of their leadership and the society they built compares to their own intentions.
It adds variety. The undertale fandom is huge and diverse, and frans lemon fanfiction offers a different take on the characters and their relationships. It gives fans who are interested in this particular pairing more content to enjoy.