What Did Neil Patrick Harris Know About The Ending?
"I never wanted to know anything about the future of the show," Harris says in the clip. "I really truly didn't because we kept getting interviewed, for nine years, all the time about when are we going to meet the Mother? Do we have any spoilers? And so I'd rather not know."
[http://www.eonline.com/news/580852/how-neil-patrick-harris-learned-of-barney-s-ultimate-ending-on-how-i-met-your-mother]
Source