Q: There is a skin for the snake that looks like the Reddit mascot?
A: You unlock all skins by sharing the game. This is found in the lower right corner in the screen. Share the game on twitter or facebook.
Make sure you disable any other slither.io extension and scripts first!
How to install user scripts?
Firefox and related browsers: Greasemonkey.
Google Chrome, Chromium, and related browsers: Tampermonkey.
Opera (version 15 and later): Tampermonkey or Violentmonkey.
Opera version 12 and earlier supports user scripts natively. Violentmonkey provides a friendlier UI and better compatibility.