RORY: You’ve met him [Todd] twice.
LANE: But the third time’s a charm.
Third times a charm is the American version of the old saying, Third time lucky. It means that if you have failed in your first two attempts, you will probably succeed on the next one.
The origins of the proverb may be ancient, as the sacred power of things in threes is older than the Trinity, and can be found in Celtic magic and even fairy tales; it is a common idea in many cultures around the world.
The Annotated Gilmore Girls 