Production
The episode's teleplay was co-written by supervising producer Josh Singer and co-showrunners Jeff Pinkner and J. H. Wyman, based on a story by Singer, Wyman, Pinkner, and consulting producer Akiva Goldsman. House M.D. veteran David Straiton served as episode director.
Fringe began casting for an actress to play Walter's wife Elizabeth in November 2009. In their report, they were looking for a woman roughly forty years old who was described as being "strong (yet broken), intelligent, attractive, likable, lovely and extremely versatile". In December 2009, Entertainment Weekly announced Irish actress Orla Brady had been cast as Elizabeth Bishop, a possible recurring character. Some critics questioned the casting, as they considered Brady to be too young and were unsure if she would appear in the present or a flashback sequence.
"Peter" was set in 1985, with a much younger Walter and Peter Bishop, and also features an appearance by Walter's wife Elizabeth. Actor John Noble used material he had created since the airing of the pilot, which he explained was his sense of "what was this man like before he deteriorated." The production crew tried different methods with the actor to create a younger Walter, such as changes to his hair, make-up, and wardrobe; they ultimately decided on using "tabs" to keep the wrinkles in his face back. He did not wear a wig, but the crew did add parts to the front and back. When asked what preparation went into playing a younger Walter, Noble explained:
"Quite a lot, but in the sense in my preparation to find the Walter that we all know now, I had to go back to him right at the beginning to see where he came from. So that process was started before the pilot really, what was this man like before he deteriorated, so I was able to revisit that. Physically, of course, what I had to do was capture the energy, to capture the physicality of the man, the vocal physicality of the man, this was my task. I was aided enormously by my hair and makeup and special effects people here in terms of getting the overall, and indeed wardrobe helped a lot as well. And then we, the shot up through these beautiful lenses that we got a different feel to the episode than we would now. All of those elements work together... to create this version that you see in the episode."
The episode was shot through special lenses to make it more reminiscent of the decade. At Peter's funeral, actress Blair Brown wanted her character Nina Sharp to wear sunglasses, because she thought Nina would not share her emotions at the funeral. Unlike Noble, Brown wore a wig. The scenes at Reiden Lake were actually shot on a parking lot, and the crew placed a covering over it to simulate the cracks normally on a lake.
To reflect the episode's setting in 1985, the typical title credit sequence was redone using different music, the Amelia font for early computer type for the show's logo, and terms that were novel science at the time, such as "virtual reality", "genetic engineering", and "personal computing". Pinkner later recalled, "One of our writers said off-handedly that if we’re doing a show from 1985, shouldn’t we do a credit sequence from 1985, and literally, we pounced on it". He and Wyman asked J. J. Abrams, who wrote the original credit sequence melody, to write a 1980s version; Abrams was "very, very happy to do that," according to Wyman.
As with other Fringe episodes, Fox and Science Olympiad released a lesson plan for grade school children based upon the science depicted in "Peter"; the lesson's intention was for "students [to] learn about the challenges of effectively communicating scientific principles and concepts, especially via non-verbal methods."
