The Three Little Pigheads are three little pigs that are the boss(es) of the Mario Zone of Super Mario Land 2. There are three of them, and each has a different "house" and a special attack. The first has a straw house, and attacks by rolling back and forth along the screen. The second little porkchop in the wooden house tries to pounce on Mario by jumping around the screen. The last, brick-housed pigheaded swine attacks by jumping, too, but leaps a bit higher every time. Below are pictures of each pig in his abode.
The obstinate little oinkers have also landed a starring role in the Mario vs. Wario comic (which is notable for being the only form of media to ever give them English names and therefore the origin of the name "the Three Little Pigheads"), where Wario ordered them to attack Mario with other Super Mario Land 2 creepies. Here, Mario (who was oblivious to the fact that Wario's monsters were even trying to harm him in any way) somehow mistook them for a bowling game and ended up defeating them by knocking one of them (which he was using as a ball) into the other "pins".