The Arrival - S1-E4
Trivia: Michael Cerveris makes his first significant appearance in this episode as The Observer/Bald Man. However if you watch the series from the beginning, he makes fleeting appearances in every episode, sometimes on a tv screen.
Inner Child - S1-E15
Trivia: The Observer September is briefly seen watching the boy as he is driven to his new home. (00:48:05)
Trivia: Olivia walks past an observer on the train while looking for the suspect. (00:42:05)
A New Day in the Old Town - S2-E1
Trivia: The observer quickly crosses the street after the car crash in the beginning of the episode. (00:00:55)
Trivia: In every episode, there is a clue for what the next episode will be about. For example, in episode seven, Samantha Loeb gives Olivia a copy of "A Christmas Carol". In the next episode, Walter is reciting Christmas carols to regain his memory.
Trivia: The story is set mainly in 1985. During a scene in the other universe, the observers are outside of a cinema which is showing Back to the Future - with Eric Stoltz as the star rather than Michael J Fox. Stoltz was originally hired to play Marty, but was fired after filming started and Fox was brought in to play the role of Marty.
Trivia: The Observer appears in the hospital. The agents walk pass him on their way to see the dead man-baby. (00:09:20)
Answer: In the time line of Season 4, William Bell is trying to destroy both universes to create a new one, and he needs Olivia to power the collapse. So he helped her escape. But the real question is, if not in search of Peter, why Olivia has to travel to the alternate universe to be captured and replaced?
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