Grandfather Paradox

"Wow. You're literally a Grandfather Paradox."

- Samantha Carter to Cameron Mitchell

The Grandfather Paradox is a paradox of time travel. The paradox is ''suppose a man traveled back in time and killed his biological grandfather before the latter met the traveler's grandmother. As a result, one of the traveler's parents (and by extension, the traveler himself) would never have been conceived.''

When Cameron Mitchell, Samantha Carter, and Daniel Jackson were sent to an alternate timeline through the Stargate due to Ba'al's actions it was found out that Ba'al had killed Mitchell's grandfather aboard the Achilles causing both Doctor Lee and Carter to comment on the fact that Mitchell was a literal Grandfather Paradox.