Ruffians are Professor Pester's minions. They rampage your garden, coughing up toxic candies, opening gates and destroying your fence, starting (and also winning) fights with your pinatas, and filling in your ponds. They will not leave unless you bribe them with money, have a BarkBark with a Spiked Collar to chase them off, or a Captain's Cuttlass. A Mallowolf can also scare them away with its howl.
Ruffians are outlaws and thought to be quite disgraceful and destructive in the Pinata world. One of Leafos's quotes shows this: "When I was little my mother told me to control my temper or I would become a Ruffian. What a horrible thing to say to a child!".
Ruffians may have a soft spot for Helpers , however. If a helper is stuck too long they will free the helper and run away with them.