Uncle Faustus is a deceased relative of The Addams Family.
When Uncle Fester was playing hide-and-boo with Wednesday Jr., Pugsley Jr., and Cousin Itt, Uncle Faustus in his grave rattled his chains, distracting Fester enough for the kids and Itt to reach home base. Uncle Fester cried foul so Pancho Addams asked Faustus if he did distract Uncle Fester. Uncle Faustus answered him by shaking his chains. Uncle Faustus likes his jokes but promises not to interfere with Fester's next search.
The television special: