Oh. Dr. Byrne dates back to my very early Duffer days, when I was primarily suffering from multiple personality disorder (well, disassociative identity disorder now). My "normal" personality was Glen. Dr. Byrne was the alter-ego who is persnickety, thinks he is a therapist, and spent a lot of time trying to cage Mewsie's cats, who frequently shot him with a tomato cannon in revenge. Dr. Byrne was continually trying to reform Glen, who had no interest in reformation.
Dr. Byrne hasn't resurfaced in a while; probably I decided he was less interesting than my nonverbal buffalo, who writes operas. Actually he was somewhat like the DLR, come to think of it, except he wasn't interested in blowing things up for universal justice, and would have tried to imprison the DLF for being messy.