"How I Met Your Mother" season 9 has been at the center of a national debate about race, following it's kung fu-based episode last week. "How I Met Your Mother" creators now reveal that they only expected the show to last for eight years, and that season 9 featuring Barney and Robin's wedding weekend has been quite a challenge.

"We really did have an eight-year plan," "How I Met Your Mother" co-creator Carter Bays told CBS. "It turned out to be nine years."

Bays said the final season has been "a challenge," but that the producers are proud of the challenge they made for themselves by setting season 9 in one weekend, the wedding weekend Barney and Robin.

According to TVLine, next Monday's episode will reveal the names of Ted and the Mother's son and daughter, played by David Henrie and Lyndsy Fonseca, respectively, co-creator Craig Thomas revealed at a farewell Q&A/reception on the show's set for members of the Television Critics Association.

Also, CBS reports that one of the final scenes in the "How I Met Your Mother" season 9 finale was shot eight years ago, with teenage Henrie and Fonseca. Worried that Henrie and Fonseca would look different as they aged, Bays and Thomas decided they wanted the kids on the couch scene to be an important component of the "How I Met Your Mother" season 9 finale.

So in 2006, "Bays and Thomas brought the young actors in, closed the set to all but one camera operator, and filmed the two-minute scene that will bring the series to a close," CBS reports.

"It's been the plan all along," Thomas said. "What you see on March 31 has been the plan. We leave the series with a certain message that we wanted to convey."

Thomas also gave another spoiler: the title of the March 31 series finale is "Last Forever." Three more guest stars were also named to appear in season 9 before the final episode: Rachel Bilson, Sarah Chalke and Lucy Hale.