'How I Met Your Mother' Cast Weighs In on Season 8 Finale, Mother's Identity [Video]

"How I Met Your Mother" is inching ever closer to revealing the "mother of all secrets." It could happen during tonight's Season 8 finale (the buildup to Robin and Barney's wedding!) as the below promo teases, or more likely, we'll have to wait until the ninth and final season of the long-running sitcom to meet Mrs. Mosby. But as Jason Segal (Marshall) put it in a behind-the-scenes cast interview, "It's gonna get weird if we don't meet the mother soon. We're gonna be, like, 60," adding, "This last episode really sets up the process of meeting the mother."

Neil Patrick Harris (Barney) is pretty confident that it will be a Season 9 reveal, saying, "My suspicion is that they're not even going to reveal the mother until the end of the series." Cobie Smulders (Robin) always imagined that it would happen in the series finale but is rethinking her stance: "I don't know; I think that it would be cool to have [the mother] integrated into the story more than that."

[Related: 'How I Met Your Mother' Finale: Will We Actually Meet Mrs. Mosby?]

Alyson Hannigan (Lily) is just relieved that the series "is going to get to have a proper ending, rather than sort of, OK, we're gonna wrap it up really quickly."

What about the mother's identity? Have we seen her before? Josh Radnor (Ted) doesn't think so: "I always thought it's not someone we've seen on the show. I don't think it's going be revealed, like, oh, it was always that one girl from Season 3. I think it's just going to be a great girl who has a yellow umbrella and plays the bass in a band." Harris suspects that whoever Ted's elusive sweetheart might be, she won't be played by some big-name actress: "I would be very surprised if it ends up being some famous guest star that we know from that other show on that other channel."

[Related: Neil Patrick Harris to Host Tonys for Fourth Time]

So what big reveals does the Season 8 finale hold? Harris shared that they're not just closer to Barney and Robin getting "legend married," but also closer to "finally consummating the relationship." Segal dished that Marshall is "going to get some resolution on what he wants to do with his life." And Radnor and Hannigan teased that Ted, who still has unresolved feelings for Robin, is looking to make a major life change. "There is a big decision," Radnor says.

To find out how the lead-up to Barney and Robin's wedding day goes down, tune in to the "How I Met Your Mother" Season 8 finale on Monday, 5/13 at 8 PM on CBS.