Well, I'm not sure specifically which Gravity Falls Taco Bell fanfics are out there, but generally, fanfics can be a great source of fun and unique ideas. It could be that a fanfic has the characters going on a quest related to a special Taco Bell item in Gravity Falls. Maybe they discover a secret menu item that has magical properties in the context of the show.
You can try looking on fanfic websites like Archive of Our Own (AO3). It has a large collection of fan - created works, and there might be some Gravity Falls Taco Bell fanfics there. Another option could be FanFiction.net.
The 'Mystery at Taco Bell' trope could also be popular. Maybe there are strange disappearances or occurrences in the local Taco Bell that Dipper decides to investigate. It could be related to some sort of supernatural entity that is attracted to the fast - food joint's unique energy.
In the 'Dipper goes to Taco Bell' fanfic, he might be on some sort of adventure and the Taco Bell is a stop along the way. He could end up getting involved in a little mystery inside the restaurant, like a missing ingredient that he has to help find in order to get his favorite taco made. He may also make some new friends among the staff or other customers.
Well, perhaps Dipper might have some strange encounters with the Taco Bell staff. Maybe he discovers a new kind of taco that has some magical properties in the fanfic.
He might meet a really chatty customer who loves to talk about conspiracy theories related to fast food. This person could be sitting at the next table and start sharing all kinds of wild ideas with Dipper.
I'm not sure which specific 'Taco Bell Bedtime Story' you are referring to. There could be many fictional or user - created stories related to Taco Bell at bedtime. Maybe it's about a person who dreams of Taco Bell after a long day and all the delicious tacos they might eat there.
One horror story could be about getting really sick after eating at Taco Bell. Maybe someone had food poisoning and spent days with stomach aches and other awful symptoms. It's a real nightmare when you expect a good meal but end up ill.