Entrada (Fringe)
"Entrada" is the eighth episode of the third season of the American science fiction drama television series Fringe, and the 51st episode overall. The first part of the third season spent much of its time alternating between the prime and parallel universes, and "Entrada" was the first episode of the season to have time evenly divided between both. In the episode, both Olivia and her doppelganger "Fauxlivia" attempt to journey back to their respective universes. John Cassini, Seth Gabel, Ryan McDonald, Stefan Arngrim, and Karen Holness guest starred. Showrunners J. H. Wyman and Jeff Pinkner wrote the episode as the "culmination of a lot of things that [they] had been working on for quite a while."