The Thinking Stone is a relic item from Mystery Mountain. It makes its first appearance in "Super Muscles Show Off." According to An Yu, it is a stone as old as time. It allows the wielder the power to mentally slow things down, but requires deep concentration to use.
The Thinking Stone is painted red and yellow and resembles a monkey. After using all its power to hold down the PJ Masks Headquarters, it now has a crack on its head.