Here's how the introduction of William Shatner's Psych character in season 6 retconned the original backstory established for Juliet (Maggie Lawson).
Psych season 6 retconned Juliet O'Hara's original backstory, which was established in her first appearance. Detective O’Hara joined Psych in episode 2 as a replacement for Anne Dudek’s character, who left after the pilot when the show was picked up by USA Network. For all eight seasons, Juliet served as one of the two main detectives and a primary love interest for one of the show’s two main protagonists, Shawn Spencer.
As Psych continued to develop Juliet over the course of the series, the show eventually introduced members of her immediate family. Similar to show’s approach to the families of Shawn and Gus, some of these relatives were played by well-known actors. In Psych season 4, Shawn and Gus learned a bit more about Juliet when it introduced her brother, Ewan. Played by John Cena, Ewan was a highly-respected and capable soldier in the U.S. military, who also appeared in Psych: The Movie. In Psych season 6, the show featured guest appearances from William Shatner and Jeffrey Tambor, who played Juliet’s dad and stepfather, respectively.
It was revealed in Psych season 6 that William Shatner’s Frank O’Hara had a troubled relationship with Juliet. Apparently, he was a con artist who disappointed Juliet numerous times during her childhood. He left them a long time ago, so Juliet grew up without Frank in her life, and has resented him ever since. This directly contradicts the backstory that was given to Juliet in Psych season 1. When Shawn first met Juliet in episode 2, he saw a photo of an elderly couple in her belongings and drew the conclusion that Juliet was a person whose parents had been “happily married for 30 years”; Juliet’s surprised reaction proved his guess correct.
The problem here, of course, is that Juliet’s parents were not happily married, nor were they together for such a great length of time. Years after their divorce, Juliet’s mother got married again, this time to Tambor’s Lloyd. Additionally, the people pictured in the photo aren’t the same actors who play her parents (which is understandable from a production standpoint given that it was years before the characters were explored further). It has been argued by some fans that the “happily married” parents mentioned by Shawn includes Lloyd and not Frank, but this isn’t an accurate description of Juliet’s relationship with him.
It’s important to note that Juliet’s parents were brought up in only her first episode, so it makes sense that the writers hadn’t fully developed her character yet. Making this change wasn’t necessarily a problem, since it created not one but two memorable stories for the series. First of all, it provided a touching story about Shawn trying to get Frank and Juliet to reconcile. Frank lied and betrayed both Shawn and Juliet with his schemes, but did the right thing in the end. Later, Psych built on Lloyd’s character as well, by revealing that he, too, had secrets. He was addicted to gambling and had legal troubles that he kept hidden from Juliet’s family in order to avoid failing them like Frank did. His hilarious team-up with Henry has been praised as one of Psych’s best episodes. So, though Frank’s character did amount to a retcon in Psych, it’s an understandable one.
