You’re the only person I know of who actually read through the tag, so congratulations, you win! Gravity Falls is an amazing show, I’m a little surprised I haven’t brought this up as a crossover before. Nevertheless, this is what I want to do with my Friday night!
Mabel: 100000% Usagi. She is an optimistic fountain overflowing with love and compassion for all living things and some sock puppets
Dipper: Ami “just put down the statistical spreadsheets for 5 minutes and have some fun” Mizuno. Great at solving puzzles and observing phenomena. Not so great at the rest of life (sidenote: Dippy Fresh, but with Sailor Mercury, please discuss)
Grunkle Stan: Cat Dad Artemis
Soos: Also Usagi, tbh. This is a world of Usagis in a non-Usagi world
Wendy: Teen rebel Haruka, cooler and older than you
Ford: Cat Mom Luna???
Candy: maybe the one and only small strange Hotaru
Grenda: Makotoooooooooooo
Old Man McGucket: future ghost hologram king endymion, warning of the end-times in the vaguest manner possible
Li’l Gideon: Gangster Iron Mouse
Bill Cipher: Like, some kind of unholy blend between Professor Tomoe’s absurdist comic relief and Galaxia’s reality-altering nonchalance
Pacifica: Rei, even though Pacifica’s meanness is antagonizing and not based in friendship
Waddles: Diana
Blendin Blandin: SAILOR PLUTO
AND THE TIME BABY IS CHIBIUSA
Tad Strange: Naru
Anyway this gave me more trouble than I thought it would. Let me know your preferred cast below!