"Well, I've known for quite some time," she told Jimmy Fallon. "I didn't know how it was going to unfold. I'm concerned for many people, including myself. So yeah, I've known for quite some time and it's been hard, of course, to keep the secret."
For those who missed it, here's what happened (warning: spoilers ahead): While Kevin (Justin Hartley) and Madison (Caitlin Thompson) were set to tie the knot, she called off the wedding and they didn't actually get married. But, thanks to a flash forward, the episode still showed a member of the Pearson family saying "I do."
Skipping several years into the future, Kate (Metz) is seen getting remarried to her boss Phillip (Chris Geere).
The wedding suggests Kate and her current husband Toby (Chris Sullivan) ultimately divorce. Fans have seen the couple go through their ups and downs for quite some time. And in the latest episode, Toby tells Kate he's taking a job that would require him to be in San Francisco for most of the time while she stays in Los Angeles.
The flash forward also hints that Nicky (Griffin Dunne) marries in the future and shows Randall (Sterling K. Brown) being featured in a magazine article titled "Rising Star."
Of course, fans will just have to stay tuned for the sixth and final season to see how all of the characters' storylines wrap up. And when Fallon asked Metz if she ever wished she could just have a "normal" season, the star didn't have to think twice.
"No," she replied. "I'm not doing that to [creator] Dan Fogelman."
(E! and NBC are both part of the NBCUniversal family).