According to one version the Bullfrog was always ridiculing the great gambler Ûñtsai'yï, (Brass) until the latter at last got angry and dared the Bullfrog to play the gatayû'stï (wheel-and-stick) game with him.
Whichever lost was to be scratched on his forehead. Brass won, as he always did, and the yellow stripes on the Bullfrog's head show where the gambler's fingers scratched him.
Another story is that the Bullfrog had a conjurer to paint his head with yellow stripes (brass) to make him appear more handsome to a pretty woman he was courting.