The Silence Snake is a sock puppet that Mr. Small uses to scare kids into being quiet, whether they like it or not. In "The Sock", he does this to Gumball and Darwin, both of whom gained a fear of speaking whenever the Silence Snake is around.
The Silence Snake is a green sock puppet. Its "mouth" is purple as well as the heel. It has a red felt tongue that dangles out of its mouth. There are buttons on the heel meant to resemble its eyes.
Although the episode in which The Silence Snake appears is named after it, it is a minor character in the episode.