Sprunki began as a fan made mod of the music game Incredibox in 2024, with creators inventing numbered horror phases for its cartoon characters. Fans kept raising the numbers to absurd levels, and Phase 67429 leans into that joke by mashing the viral 67 meme into the title. It circulates on soundboards and short video edits alongside other brainrot slang like six seven, rizz and sigma, used less as music and more as a shared in joke about how massive and cursed the next phase will be.