"How I Met Your Mother" Kids knew series finale this whole time! Facebook Wed-02-Apr-14 20:45 Share this Actor Josh Radnor's onscreen children in HOW I MET YOUR MOTHER knew how the hit U.S. series would end nine years ago, after producers revealed all to them at the very start of the show.David Henrie and his TV sister Lyndsy Fonseca have been filming reaction scenes to the relationship tales told by Radnor's character Ted Mosby since 2005, when they were teens, and they continued to make non-speaking appearances in the sitcom until their brief dialogue at the very end of the series, which wrapped for good when its season nine finale aired in America on Monday.Actress Cobie Smulders, who played Mosby's on/off love interest Robin Scherbatsky, reveals, "(Creators) Carter (Bays) and Craig (Thomas), are so smart. They had actually planned the ending during our pilot."They shot some scenes with the two children - we shot it with them when they were teenagers and now they're in their mid-20s - we shot this whole scene with them."It's kind of amazing that it's been nine years and it's come full-circle and they (Bays and Thomas) have been allowed to see their vision through."But actor Henrie admits it hasn't always been easy to keep the show's ultimate plot under wraps for so long.He tells Yahoo's The Insider, "I'm 24 now, but when I turned 21 I started going out with my buddies. Everyone was always asking me, 'Dude, who's the mum? Who's the mum?'."People would try and bribe me with all sorts of alcohol, but I kept silent. I didn't tell anyone. I didn't even tell my mother." His secrecy vow paid off - the show, which also starred Alyson Hannigan and Neil Patrick Harris, attracted a series-high ratings explosion with 12.9 million U.S. viewers tuning in to watch the finale.wenn.com You May Also Like Alternate ending for How I Met Your Mother leaked online Neil Patrick Harris & Hugh Jackman have a "Host-Off" at the Tonys What Neil Patrick Harris works out to Become a fan of The Edge on Facebook and on Twitter .