Men, when they are little, like to fart. When they are old, they become an old fart. Meaning: Kids (namely boys in America) sometimes like to play the fart game (search for Eddie Murphy, the Fart Game). Haha...we will torture people and make them smell our fart (haha...do boys in China do such obnoxious things?). When a man becomes very old, he can be nick named an old fart because sometimes they cannot control there smell (they fart a lot...or worse). Sorry, more of a joke then a riddle.