Factual error: Earth's Stargate is dialed up more then once in series 1. Mostly in the first episodes, the passive gate is also shown with a rotating dialer ring when being called. This is not correct. The called gate only illuminates the chevrons.

Plot hole: When Apophis first enters SGC at the beginning, the worm hole shuts down. Then the fight between the SGC personnel and the Jaffa takes place. The scene then switches to some other part of the complex and back again. Suddenly there is an outgoing wormhole established. It is made clear throughout the show, that only very few aliens like the Asgard or the Nox can just establish a wormhole by waving the hand. Earth neither has a DHD (which is known to Apophis) nor does Apophis have access to the gate controls or was there enough time for the Jaffa to dial the gate by hand. Even assuming the scene switches giving enough time to enter the control room, the Jaffa can not be familiar with earth technology as to know how to initiate a dialing sequence on the computer.

Factual error: Carter claims that the gates shift position because of the expansion of the universe. Gravity sources within a galaxy completely compensate for such expansion. The gates would still experience "stellar drift", which is mentioned earlier in the same episode. Stellar drift occurs because stars orbit the galactic center independently.

Revealing: When Daniel, Jack, and Sam first meet the robed Jaffa in the woods, you can see the camera light in Daniel's glasses.

Revealing: When Apophis' queen goes back into the female Jaffa, it is obvious that the film footage was just played in reverse.

Other: When O'Neill first goes to visit Teal'c in his cell the symbol of Apophis on Teal'c's head is upside down.

Other: Before the last cevron locks & the wormhole engages, Carter asks "Where's the iris" to which Hammind responds "Someone used a remote, whoever it is has our codes". All well and good, except without the wormhole being active, they wouldn't be able to receive the code.

Revealing: When Hathor turns Jack into her first new Jaffa, you can see the line between his chest and the prosthetic that gives him the Jaffa "pouch".

Revealing: When Carter is looking up Hathor on the Internet, the address bar says that the web page is on the C drive of the computer. That is a really stupid mistake, since it is extremely easy to hide the address bar.

Plot hole: After Cassandra has her first "heart attack" you see her in her room. Why isn't there one of those heartbeat monitors in her room?

Revealing: When Daniel is talking to Teal'c in the jail cell, you can see a camera light reflected in Daniel's glasses.

Revealing: When Daniel is talking to the leader of the Tolan, you can see the camera light reflected in his glasses.

Continuity: When the Jacks are talking to each other right at the end, the camera goes back and forth from looking over each of their shoulders at the other one. If you look closely, the false Jack's earlobe structure changes when we see him from behind.

Other: When attempting to dial out about 26 minutes into episode, the Earth gate point of origin symbol locks (indicating that all the symbols are finished encoding). But then "chevron 2 encoded" is announced.