In the game I'm running there was a drow mook that the party captured to interrogate and ultimately befriended. Coming up with a name and personality for a non-character that I expected the party would kill within a few minutes of meeting was odd enough, but one of the players seemed to really like what I came up with despite my efforts to make her come off as unpleasant. So much so, that her character ended up forming a close friendship with the drow, which later resulted in the two forming a romantic relationship. That player even drew a little portrait of the drow, which wasn't what I imagined but was so cute that I decided it was 100% accurate.