In Chrétien's Perceval, the Fool or court jester and the maiden struck by Kay usually appear together. The Fool it was who used to say of the maid that she would not laugh until she saw the man who would be the supreme knight. This seems a prophecy in Chrétien's work (Ruth Cline cites evidence that it might once have been a geis, or magical injunction), and Chrétien's Fool proceeds to prove his prophetic powers by predecting that, for striking the maid and kicking the Fool himself into the fire, Sir Kay will in the fullness of time receive a broken arm from the avenging Percivale.
This warning the jester gleefully repeats every time Percivale sends someone to court with the message that, if he lives, he will avenge the maiden Kay struck, until it must come as rather a relief to the seneschal when it finally happens.
I feel far from confident, however, that the Fool of Chrétien's Grail romance should be automatically identified with Malory's Dagonet.
Dagonet | The Legend of King Arthur
Gerflet | The Legend of King Arthur
Roccetto | The Legend of King Arthur
Verrine | The Legend of King Arthur
Fool of the Forest