Yesterday's Enterprise - S3-E15
Question: The ever-popular gag in this episode is that Worf consumes prune juice for the first time and declares that it is a "warrior's drink," to Guinan's amusement. However, Worf was adopted as a child by human parents, he grew up on Earth, he was highly educated and graduated Star Fleet Academy on Earth. Given the reputation of prune juice as a natural laxative throughout human history, how could Worf not know what prune juice is, having lived most of his life on Earth?
Answer: There's nothing to indicate that Worf had never heard of prune juice before, just that he had never tried it before. He doesn't recognize the smell or taste of the drink as prune juice because he's never had it before. But that doesn't mean he has no idea what prune juice is, or that it is used as a natural laxative. In a later episode Guinan directly asks Worf's parents why he never had prune juice prior to her serving him the drink. They answer that as a child Worf refused to eat human food of any kind, everything he consumed had to be Klingon. Other episodes show that Klingons tend to despise human food in general for being bland. It stands to reason that someone who shows no outward interest in human food might not know what prune juice is usually used for. But then again, maybe he does know and he doesn't care because prune juice is delicious to him.
BaconIsMyBFF
Thanks for reminding me about that later episode, although I think the later prune juice explanation from Worf's adoptive parents was scripted to address many fan questions along the same lines as my own.
Charles Austin Miller