Which one episode most breaks your suspension of disbelief and keeps you from enjoying the storyline? I see this was already touched on briefly in a thread specifically about whether ESP in humans is believable. My #1 for this has always been Mudd’s Women in the very early first season, even though overall this was the most realistic and fun period of the show, when it really did seem to be set in a futuristic workplace with co-workers socializing and coffee cups strewn about. Even back in 1966, I knew that you could not swallow a pill and have that pill comb and style your hair and apply false lashes and lipstick to your face. Each time it happens the transformation still brings a frown to my face and an “oh, please” from my lips. It was an interesting idea for a story but hard to translate to television without over-reliance on the makeup artist which then made it ridiculous. I guess I give them kudos for even attempting a psychological story like that in the first place. So which episode throws cold water on you and brings you back to realizing you're sitting on your own couch?