The Fountain of Riddles is a living fountain that can answer any question, but only in riddles. He appears in the 1990 Sesame Park special, Basil Hears a Noise, as a part of a bedtime story told by Dodi.
A mysterious person has been playing tricks on the Creatures of the Forest, and King Elmo declares that the Fountain of Riddles might know who it is. They turn to humble shepherd Basil, disguising him as a minstrel (much to his chagrin), and send him and his lambies to find the fountain. After meeting Sir Louis and getting separated from him, Basil and his lambies finally come across a goblin reading a book and sitting atop the fountain. Sir Louis returns and scares the goblin away (thinking he was bothering Basil and the lambies).
The fountain awakens and gives them a riddle: "What wears a black pointy hat, a black dress, rides a broomstick, and is usually in a very bad mood?". Basil and Louis aren't able to figure it out, so the fountain gives them another hint: "It starts with W and rhymes with ditch." Once Basil and Sir Louis determine the answer and realize there's a witch in the forest, they run away in fear, leaving the Fountain of Riddles to be at peace.