While both have to very different meanings, both have a definition of meaning something small (alley - small passage, pony - small horse, pour, or amount of money). Both are 6 letters, but when made plural, are spelling differently (alleys - just add s, ponies - drop the y, add ies). Both are Latin in origin, changing letter to French. But alley is late middle English, with pony being from the mid 17th century.
