watch 01:11 The Loop (TV) Do you like this video? This needs a stretch. (Feel free to remove when satisfied of completion.) The headquarters was the hideout of Mastermind. History The New Scooby-Doo Mysteries Insert details here. Appearances The New Scooby-Doo Mysteries 104(a). Mission: Un-Doo-Able Retrieved from "https://scoobydoo.fandom.com/wiki/Mastermind%27s_headquarters?oldid=306670" Categories: Articles needing expansion Headquarters The New Scooby-Doo Mysteries locations Community content is available under CC-BY-SA unless otherwise noted.