"The fool is not expected to grasp social conventions and thus is left to enjoy relative freedom, particularly in his or her freedom of speech."

Upon taking the guise of "The Fool" you will appear to any passerby in the form that appears the most harmless and helpless to them (a gravedigger, an old beggar, a slow-minded servant, or a court jester) which you can only uncover by looking in a mirror while under their gaze. In the company of many people, you will take the form that appeals to the largest number of them. People will not go to any lengths to hide information from you and answer your questions with out guile.  

Under this guise, NPCs assume you have low status, low intelligence, and are incapable of harming them. Insight checks against you have disadvantage and must beat your spell DC to spot your true form. 

Any insults or information offered in conversation is taken with little seriousness. 

When you cast this spell at 3rd level, creatures that are immune to charm are not effected and see through the disguise immediately.

When you cast this spell at 5th level, it works on creatures that are immune to charm. A successful insight check at disadvantage can still reveal your guise.

At 7th level, creatures with truesight also roll insight with disadvantage against spell DC.