After filming Psycho, Janet Leigh avoided showers for the rest of her life. (So if you found that scene scary, you're in good company.) (Source)

Janet Leigh's daughter, Jamie Lee Curtis, starred in Halloween (1978) one of the most famous slasher films inspired by Psycho. There's apparently a genetic disposition to have someone come after you with a knife (on film). (Source)

Hitchcock wasn't fond of actor John Gavin, who plays Sam. Still, Gavin got the last laugh by going on to be Ambassador to Mexico in the 1980's. (Source)