S5E18: Meet the Quagmires
I think I can explain it to you, Peter.
This line represents the normal flow of events.
Here's where you met Lois, here's where you got married,
and here's the present. And here's the night at the bar.
Now, at some point during that evening,
you did something that changed the course of your history,
causing the time line to skew off into an alternate tangent,