The reflection of young Norman Bates in the doorknob when he flashes back to his mother's poisoning is Anthony Perkins' son Oz Perkins.
The original house set was used and the motel was reconstructed.
At time-code 25:10, when Mary and Norman Bates first go into Norman's mother's room, before they turn the lights on, you can see Sir Alfred Hitchcock's silhouette on the wall to the far right.
Producer Hilton A. Green originally suggested Jamie Lee Curtis to play Mary Loomis because of her being the daughter of Janet Leigh and having success with Halloween (1978). Jamie Lee Curtis had a scheduling conflict though, and did not want to return to the horror genre after getting such a huge role in the year's top comedy, Trading Places (1983).
The original shower head used in Psycho (1960) was supposed to have been used in this sequel as well. However, just before filming was to commence, someone stole it.
Richard Franklin: As a man standing playing an arcade video game, Battlezone, in the diner that Norman Bates works in, with his back to the camera, but turning his head briefly showing part of his face.