Continuity mistake: Carter and Cadet Haley enter the Stargate and we see them through the "puddle." When they come out on The Other Side, their positions are reversed.
Beware the Third Wish - S1-E31
Continuity mistake: The Wicked Wisher throws giant exploding coins onto the field TJ is on, as TJ runs towards the WW. The giant coins remain on the field after they explode, yet when TJ reaches the top of the field, there is no sign of the coins, or their remains.
Continuity mistake: His Shadow's ship, The Fore Shadow, begins to blast the Brunnen-G planet and the shots hit the surface causing massive instant damage seen and heard from space. Each hit charring the ground. When the camera cuts back to the planet a few shots later as the ship continues to fire, the destroyed areas of the planet from before have all moved around, with the giant char marks being inconsistent in where they landed. (00:02:25 - 00:03:10)