You should begin with a clear idea of what makes your Undertale AU different. Develop interesting character backstories and interactions. And make sure the dialogue is engaging and fits the tone of the comic.
Perhaps a story where a character reacts to the dangerous creatures in Amphibia. They initially fear them but then learn to co - exist with them. This could involve a lot of character development as they overcome their fears and discover the true nature of the creatures, which might not be as menacing as they first seemed.
Give your character a clear backstory. If they are from our world reacting to Amphibia, explain what led them to this new world. Maybe they were drawn by a mysterious force because they have a connection to Amphibia in a past life. This backstory will influence their reactions and decisions throughout the fanfiction.
One popular Amphibia fanfic could be those that explore the backstories of the main characters in more depth. For example, a fanfic might focus on Marcy's life before coming to Amphibia and how her love for games influenced her actions. Another type could be adventure - based fanfics, where the characters embark on new quests not shown in the original series.
The 'amphibia graphic novel' might center around the main characters from the Amphibia series. It could show their growth throughout the story. For example, it may illustrate how they adapt to the new environment in Amphibia, face various challenges like dealing with strange creatures and difficult terrains, and form bonds with the local inhabitants. This all might be presented in a vivid graphic form, making the story more engaging.
The characters in Amphibia have distinct personalities. In tickle fanfic, their reactions to being tickled can be a great way to show their personalities. Anne might react with her usual bravado and humor, while Sasha could be more resistant at first. This interaction between character traits and the tickle concept makes the fanfic unique.
If it follows the TV show Amphibia, then Anne, Sprig, and Polly could be the main characters in the 'amphibia graphic novel'. Anne is the human girl who gets transported to Amphibia. Sprig is an adventurous frog who befriends Anne, and Polly is Sprig's younger sister. They are likely to be central to the story in the graphic novel as they are in the show.
There are Amphibia OC fanfictions where the OC is a lost traveler from a far - off land. In these stories, the OC often has unique abilities or knowledge that either helps or hinders their journey in Amphibia. Some might involve the OC teaming up with Anne, Sprig, and the others to uncover secrets about Amphibia that were previously unknown, like hidden ancient ruins or the true origin of the Calamity Box.