This is where I started seriously watching Fringe! Fun story: during that episode where they swap, my dad had to pause in the middle to take me to the airport. In the car, I told him, "They brought the wrong Olivia back." he raised his eyebrow at me and asked how I knew. I told him narrative structure made it obvious.

When my plane landed, I had a text from my dad: "You were right about Olivia!" XD I was very proud of myself.

The resolution of the AU Olivia/Peter thing is...I'll just say that I really enjoyed it for several reasons.