Why was Dr. Klein's name changed?
Browsing through the novel just now, I noticed that Dr. Klein's first name is Sam, whereas it's Harold in the film. "Harold, help me!" yells the hypnotist in the film whereas it's "Sam! Sam, help me!" in the novel. Just a memory lapse by Blatty? He couldn't remember Klein's first name when doing the script, so he just inserted anything? And, while it's probably nothing, I can't help noticing the Howdy-Howard (dad)-Harold similarity.