Notes:

My edit based on this picture of Gravity Falls creator Alex Hirsch and the hiatuses the show has had including its current one. Most text is from the theme song, but "Disney Channel" is a stylized version of the channel's logo in the promo short for the show called "Creature in the Closet".
Text sources:
"Alex Hirsch": theme song title card ("created by Alex Hirsch")
"tri": theme song title card
"e": "Alex Hirsch"
"s t": theme song title card
"o": "Alex Hirsch"
"ta": theme song title card
"k": Mystery Shack sign (theme song)
"e": "Alex Hirsch"
"a": theme song title card
"p": "Dipper" (theme song)
"iss": theme song title card
"bu": "created by Alex Hirsch"
"t": theme song title card
"Disney Channel": Disney Channel logo from "Creature in the Closet"
"p": "Dipper" (theme song)
"u": "Alex Hirsch"
"t": theme song title card
"his bod": "created by Alex Hirsch"
"ily f": theme song title card
"u": "Alex Hirsch"
"n": "Stan" (theme song)
"c": "created by"
"ti": theme song title card
"o": "Alex Hirsch"
"n": "Stan" (theme song)
"s": theme song title card
"o": "Alex Hirsch"
"n": "Stan" (theme song)
"hi": "Alex Hirsch"
"at": theme song title card
"u": "Alex Hirsch"
"s": theme song title card