Psych had a reputation of having a humorous obsession with pineapples, but many fans have wondered why. The tropical fruit made multiple appearances throughout the USA series, and the show’s attachment to pineapples even extended to promotional photos of the cast, comic con conventions, and merchandise. Through its eight-season run, Psych made use of a number of recurring jokes and gags. These included Shaun’s long list of fake nicknames for Gus (Dul Hill), references to popular movies from the 1980s, Gus’ “Magic Head” moniker that originated in a season 1 episode, and many more.

https://screenrant.com/psych-pineapple-gag-origin-true-story-explained/