Fool is the mysterious spirit of the stage. He is about the size of an action figure, and appears as a type of jester or clown. He appears to Sora shortly before she appears on the Kaleido Stage for the first time. Fool is invisible to everyone but those who are destined to do great things on the stage and/or whose heart is completely dedicated to the stage. He seems to be the spirit of a true jester who once was devoted to a princess who never smiled.

Although a spirit, Fool is a pervert who tries many times throughout the series to see Sora, and sometimes her friends, naked (usually by suggesting that they should take a shower). Sora is quick to prevent Fool from peeking in any given situation by trapping him somewhere or rebuking him forcefully, most often in a comedic, slapstick fashion. Later in the first season, Layla becomes capable of seeing Fool as well; the same happens to Rosetta at the end of the second season, who takes his advice more seriously than Sora, most of the time where Sora can tell he is only doing so to satisfy his perversion.

In his more useful moments, he acts as a fortune teller, revealing possible futures to Sora (in the first season he reads the future from tarot cards, in the second season he reads and reveals the hidden workings of intercharacter relationships via astrology). He is also the one who explains the inner mechanics of the Mystical Act to Layla and Sora in episode 25, An Amazing Bond.