In the Stargate SG-1 episode "200", there is a sketch showing SG-1 meeting the Furlings (which ends with Sam saying "Well that never happened!").
There are a few scenes that look like they were reused from previous seasons, like the Deathgliders getting shot up (one of the season opening credits used it). I also suspect that Teal'c saying "we led them straight here" was stock footage since he is without hair in that clip, but "200" was a Season 10 episode and he was on his third season with hair.
Which episodes did this sketch pull stock footage from?