At the end of an act of anal sex, when a penis is removed from an asshole, sometimes the penis is covered with shit and with kernels of undigested corn. This phenomena, as well as the penis in this situation, are known as "corn dick". Corn, if not chewed up, is not easily digested and so appears as whole kernals in feces, which then sticks to the penis in anal sex. Corn dick can generally be prevented with enemas.
You bottoms had better clean your shit 'cause I don't want no corn dick when I fuck you.