As promise.. yesterday... that I'll post :KELISILA JATAKA [www.jathakakatha.org]
Brahmadatta, king of Benares, could not look upon anyone old or decrepit without playing jokes on them. He made old men roll about on the ground and played practical jokes on old women. His friends behaved likewise. All old people left his country; no parents or aged persons remained to be tended by the young, and newcomers among the gods were few in number.
Sakka (the Bodhisatta), wishing to teach the king a lesson, once appeared before him in the guise of an old man, with two jars of butter milk in a crazy old cart, having willed that only the king should be able to see him. The king was riding his state elephant, and when he asked the old tarter to move the latter dashed the two jars on the kings head and the onlookers laughed to see the milk dripping down his face. Resuming Sakkas form, the Bodhisatta admonished the king.
****** The story was related to account for Lakuntaka Bhaddiyas deformity. J.ii.142-4.