Wonderhoy comes from Project Sekai Colorful Stage, the 2020 rhythm game featuring Hatsune Miku and original idol units. It is the catchphrase of Emu Otori, a relentlessly cheerful performer in Wonderlands x Showtime who uses it as a greeting built from wonder and ahoy. Fans clipped her voice lines from the game and edits, and the short exclamation spread through anime and rhythm game communities. Its brevity and unmistakable tone keep it popular as a ready made burst of joy.