Ted Mosby (Josh Radnor) sits his son and daughter down to tell them how he met their mother. That’s the way “How I Met Your Mother” began, on Sept. 19, 2005. Nine seasons and almost nine years later, Ted is less than 48 hours from getting to the point. It’s a tossup which is more impressive here: that a sitcom could last 200 episodes with what sounds like a one-idea premise, or that a parent could keep his kids listening to him talk about anything for nine years. But if Mosby’s kids wanted the answer, they didn't have much choice....