Xavier's left hand is a snake from the elbow down. It usually acts as a regular hand, but in the episode "6th Teat of Good Intentions" it speaks directly to him. It seems to have an affinity for human flesh, as in that same episode it eats a total of 7 babies.
When Snake Hand speaks it comes out as garbled noise, but it is translated by a narrator. Rather than giving a literal translation of what Snake Hand says, the narrator just gives a basic summary of Snake Hand's statements. He uses it to masturbate with frequently.