The Mockingbird is the rudest resident of Falderal. He nests in the tree in the town square and insults all passersby. Valanice was the recipient of a multitude of insults, until the cheese moon landed in the fountain and scared the Mockingbird out of his nest. Valanice discovered a wooden nickel in his roost.
The Mockingbird served no real purpose other than to hide the wooden nickel in King's Quest VII: The Princeless Bride, although he provided some humor in the already wacky town of Falderal.