There once existed a video of someone reading a Gravity Falls fanfiction known
as "Dipper Goes to Taco Bell." It was originally uploaded somewhere around 2012
as evidenced by the Know Your Meme article and other sites such as Funnyjunk.
However, said video was removed from Youtube along with the creator's channel
sometime before or after 2015. Many other readings of the same fanfiction exist, including a popular one by Brendaniel which was also removed sometime around 2018 (this one was reuploaded however.)
The narrator of the video was doing a classy, professional sounding voice, as well as voices for the characters involved, while a female actor voiced Dipper's sister Mabel. One of these voices included a very deep, creepy tone with a sort of accent for the "Taco Bell Employee." Another detail worth noting is use of music in the background throughout the video, including the song "Dombummel", often heard in episodes of Spongebob Squarepants.
Evidence of Existence
While the video itself has been lost for years in it's original form, it still exists online in the form of a reaction video on Youtube. The video in question, titled "Dipper Goes to Taco Bell Reaction Video" by CuJoProductions is of the uploader reacting to the original upload of the fanfiction reading to Youtube. However, there is commentary as it is a reaction video, and the uploader doesn't watch the entire video due to it's graphic nature.