I think the more relevant "how" is: How exactly are the producers going to keep this premise going for two, three, four or more seasons? Well, obviously they have a plan, and it couldn't be any more complicated than the one those so-clever-it-makes-you-sick producers have for Lost. So Ted (Josh Radnor) is a 27-year-old Manhattan architect who, 25 years now, will sit his surly kids down to tell them how he met their mom. The story starts in 2005 because this is when his buddy, Marshall (Jason Segel), proposed to his longtime girlfriend, Lily, who's played by Alyson Hannigan. Dear, sweet Alyson Hannigan. After seven seasons on Buffy and the American Pie trilogy, she has a nearly fanatical following. Why? Because she's pretty/cute but she seems down to earth and, most important, has a massive geek appeal that makes dudes think, "Yeah, I could totally get her if we could just hang out for a little while." Plus guys love flutes.
But back to the story. Nice twist at the end. So Robin (Cobie Smulders) is actually their "aunt"? Well, that's just weird. After all, who doesn't love to hear a tale about your dad hooking up with your aunt? Bleh. Then again, I noticed that "Ted" (voice of Bob Saget in the 2030 scenes) referred to his friends as "Uncle Marshall" and "Uncle Barney." So maybe it's not the sister. Maybe it's some other girl we'll meet later who is also cool about the phrase "Smurf penis." Suit up!