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: Kai orders his squadron to bring up their stingers on their bug ships, and in a side angle shows them curling up like a scorpion stinger. It then cuts to a close up of one stinger opening and it suddenly changes shape a little. In the side angle it looking more like a shark head with a visible hump on the bottom side, to being almost a perfect round football like shape in the close up. Also the space gas around the ship changes from green to white between shots. (00:02:35)