You might know what episode certain major events happened in, who was in a relationship with who and even who said what, but how much attention did you really pay to the decade-long sitcom?
Sure, we spent a long time with them and watched them grow from naive twenty-somethings into romantically stable, sometimes even mentally stable thirty-somethings. They won at life and we cheered them all the way.
But that doesn't mean you knew them as much as you really though. For instance, could you say you knew the characters by their actions and their pasts? Could you pick out which of the female characters any one hint is pointing towards no matter how vague?