The patron known as Mrs. Quaalude is actually one of the nicest people you'd ever care do deal with and is certainly not a "rogue" per se. She is however a difficult person to deal with in that everything takes three times as long to explain to her due to her brain seeming to be in a fog. I don't know that Mrs. Quaalude is necessarily medicated, but it would sure explain a few things. Not only does it take longer for her to understand things being said to her, it takes her a long time to communicate to others because her speech is very... very... slow... and... her... voice... so... very... very... low... and... tranquil... like...a slower... female version... of the... Hal 9000. You can feel yourself... getting... drowsy, just talking to her... as though the condition is... psychically... contagious.
While Mrs. Quaalude does check out the occasional book, her real claim to infame is as a computer patron. She used to come in weekly to check her email or otherwise surf the net, but for a very long time she needed assistance doing so with nearly every aspect of it. Often that assistance came in the form of her daughter, who would roll her eyes and explain to her mother, for the umpteenth time, over the course of 15 minutes, how to find H0tmail. A few months later, though, her daughter went all goth-chick on us, which meant that while she would come to the library she was way too cool to hang with mom anymore, so it was up to the "liberry" staff to help Mrs. Quaalude navigate the mysteries of the web. To Mrs. Quaalude's credit, our lessons did eventually take and by the time she stopped showing up as often she rarely needed help at all.
I know for a fact I've had several noteworthy and frustrating experiences with Mrs. Quaalude, but because I failed to write them down, (or perhaps because of her psychically contagious brain fog), I cannot relate them here even from memory.