Ooh."Crusade", season 9. When Vala's angsting about having become pregnant without sex, and asks if any of them have heard of anything like it, and Sam and Cameron exchange looks, and Cam says uneasily, "Well, there's one ..."

Teal'c (very seriously): "Darth Vader."

(I especially love the fact that Vala asks how that turned out, and Teal'c is clearly about to start explaining the plot of the prequels to her.)