Chrissy Metz went to the mat for her co-star Chris Sullivan, who wears a "fat suit" to play her funnyman fiancé Toby on "This Is Us."
During Thursday's "Watch What Happens Live with Andy Cohen," Metz, 36, said hiring anyone other than Sullivan, 36, would have been silly because he was "the best man for the job."
More Pop Culture videos
Watch Tish and Brandi Cyrus show their differing design styles live on TODAY
Get a sneak peek at ‘Despicable Me 3’ (and at Dylan’s baby Calvin!)
Tish and Brandi Cyrus talk about their new design show (and Miley’s old room)
Personalized travel bags and photo canvases: Steals and Deals for Father’s Day
“We tested a lot of gentlemen who were bigger, and I get it — people think the authenticity is kind of ruined by that. But Chris has been heavier, so I think he understands the plight of being overweight,” the actress explained.
Metz said Sullivan was perfect for the role of Toby, even if he required a little extra padding.
"People wear prosthetics all the time — it’s just weight as opposed to, like, a nose or a chin,” she said. “It’s just kind of the name of the game.”
Metz herself wore prosthetic padding when she portrayed "fat lady" Ima Barbara Wiggles on "American Horror Story: Freak Show" in 2014.
Metz's character, Kate Pearson, has struggled with her weight throughout her life. Sparks fly when she meets dapper dresser Toby in a weight loss support group, and the two fall in love.
The actress, who was nominated for a Golden Globe this past December, revealed to talk show host Ellen DeGeneres that she's excited to lose weight along with her character, and signed on to the part knowing that was a possibility.
"Like most actors, we are chameleons. We play different roles. Like Christian Bale lost all that weight for 'The Machinist," Metz told DeGeneres. "So I was like, 'Oh, I hope I get to lose weight. Because that's a win-win for me."