Revealing mistake: As we know, the watery image of the event horizon is projected onto a blue backdrop. Ger'ak comes through the Stargate and we can see the image of the event horizon, though faint, around and above the Stargate itself and is not confined to normal area for the event horizon. Blatantly visible if you look for it on the airing of the episode on the Sci-Fi network.
Stronghold - S9-E14
Continuity mistake: Season 9, episode 14 "Stronghold": When Bratac has cleared the gate in his alkesh, there is a shot of the gate from nearly side on. There is no wormhole, despite the SGC dialing it less than a minute before.
Other mistake: Teal'c says "Mother ships do not possess cloaking capabilities" But Apophis in season 4 had cloaked Mother ships.
Revealing mistake: When Carter says "It will just take a few minutes to initialize" at the super-gate and presses the screen on her hand you can see for a brief second that it is a video recording since the options for play, pause and stop show in the options bar on the screen. (00:36:30)
Continuity mistake: When SG-1 is tied up, Carter has blood going down her cheek and from her mouth right before being beamed up. In the next shot on board, the blood is gone.
Continuity mistake: When Col. Mitchell is talking to Col. Carter in the control room, the initial shot shows Carter appearing on a white computer display. The scene then cuts to a close up of the conversation and the display is black. It is also much thinner than the white display. (00:11:45)
Stronghold - S9-E14
Revealing mistake: Just after Sam shouts to Mitchell to wait for back up, there is a side shot of a soldier firing a machine gun. There are cases going into the gun without the actual bullet in them, showing they are blanks.
Chosen answer: Report 30185 is a joke report referring to the time when SG-1 go back in time to 1969 in the episode '1969'. The joke is that Colonel O'Neil knocked up a hippie and made sure Mitchel was taken care of throughout his life, like how he got into the 302 program while his buddy, a better pilot, did not.