1: Watch the Stargate SG-1 episode 'The Enemy Within'
2. When Col. O'Neill enters the room Teal'c is mediating in, and the shot focuses on Teal'c, the snake on his gold tattoo is arched upwards.
3. The next scene Teal'c appears in, the snake had flipped, so it forms a 'u' shape, as it does in every other episode. It flips again at least once throughout the episode.