Basically, a joke that originates from a shitty video in which sans and nagito komaeda dance with the hallway that has sans in it in the background, with the song "fingers in his ass" playing in the background, which was discovered on a Sunday, afterwards creating Fingers in his ass Sunday.
"damn, it's fingers in his ass Sunday! Time to watch that video again!"
by Jeef The Dumbass May 16, 2022
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