How I Met Your Mother ends its nine-season run tonight. 

There are a lot of theories about what will happen on the series finale. One rumor is that Ted has been telling his kids how he met their mother because she has died. Last week star Alyson Hannigan told Jimmy Kimmel that the finale has "a surprise ending," though she didn't give any details. She said, "I think the writers really wrapped it up the way the fans wanted it to be wrapped up, and they're going to answer all the million questions that everybody has. And more."

What we know will definitely happen on the one-hour episode is that we'll finally learn how Ted met his two children's mother.