If their (SG-1) memory was erased prior to dialing back to Earth, they would never transmit the Iris Code but in each case the Iris is open. This is an error because SGC mandate is to close the Iris whenever there is an incoming wormhole. However, their memories could have been erased after sending the Iris Code.
Urgo is supposed to be invisible to everyone except SG-1. But in the infirmary when they are describing Urgo to Dr. Fraiser, the guard behind him keeps looking directly at him (and occasionally smirking).
Urgo's reflection is visible on the conference table in spite of the fact that he is supposed to be invisible to all but the SG-1 team.
Dr. Fraiser states that she cannot determine how technology was implanted in SG-1 members' brains. Considering that they are constantly "beaming" across the galaxy through wormholes created by the Stargates (and Asgard devices), shorter distances through the Rings, etc., it seems an obvious assumption that something could be beamed inside a person, but that thought is never considered. However, the very fine technology to 'beam' small objects (e.g., into a body) is never demonstrated in the series.
Urgo is within the minds of SG-1 and not able to make objects move. When he is counting for the hide & seek game however, after he gets to ten, he looks around. The chair he is sitting in moves as well.