Children of the Gods (1) - S1-E1
Plot hole: When Apophis and his Jaffas are leaving SGC with the captive soldiers - there is no way they could have activated the gate without a DHD, but somehow it gets activated, and they escape.
Cold Lazarus - S1-E7
Plot hole: Before the last chevron locks & the wormhole engages, Carter asks "Where's the iris" to which Hammond 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.
Singularity - S1-E15
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?
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 ★