Other mistake: When O'Neill first goes to visit Teal'c in his cell the symbol of Apophis on Teal'c's head is upside down.
Continuity mistake: During the surgery, when they attempt to remove the Goa'uld, they start a timer. The timer starts at 00:00:00, then it blacks out (obviously, you don't want to be bored by major neck-surgery), and then the timer is at 01:19:49. However, seconds later (after Carter and Daniel's conversation), look at the timer in the background, it reads 00:23:46. (00:32:35 - 00:33:10)
Answer: While the series was undeniably successful, filming it is a long process, taking many months of often long days. Anderson, after several years of doing this, wished to spend more time with his young daughter, who he felt he was neglecting, and requested that his role in the series be scaled back. Ultimately, he decided to leave the main cast altogether and only make occasional guest appearances.
Tailkinker ★