'This Is Us' season 1 cast news, spoilers: Elizabeth Perkins cast as Rebecca's mom; Chrissy Metz reveals upcoming weight loss

"Preacher" actress Elizabeth Perkins will take on the role of Rebecca's (Mandy Moore) mom in "This Is Us" season 1.

The actress is set to guest star as Janet Malone, Entertainment Weekly has learned. Perkins will appear in several flashbacks that involve an adult Rebecca. The "Weeds" alum is the second person to take on the role of Janet — a different actress played the part in flashbacks featuring Rebecca as a child back in episode 5.

"This Is Us" season 1 marks a reunion for Perkins and Moore, who co-stared in "All I Want" (2002). Perkins is best known for appearing in the television shows "How to Get Away with Murder," "King of the Hill," and "How to Live with Your Parents (For the Rest of Your Life)." Her film career includes roles in "Ghostbusters" (2016), "Must Love Dogs" (2005), "Moonlight and Valentino" (1995), and "Big" (1988).

Meanwhile, "This Is Us" star Chrissy Metz has revealed that her contract for the NBC dramedy includes a weight loss clause. This confirms that her character, Kate, will eventually accomplish her goal of getting fitter and healthier.

"In our contract, it did state that that would be a part of it, to lose the weight in the trajectory of the character as she comes to find herself," Metz told TV Line. The actress called this a "win-win" situation for her as the clause gave her additional motivation to follow a healthier lifestyle.

In the latest episode of "This Is Us" season 1, Kate and her boyfriend Toby (Chris Sullivan) were both trying to lose weight. But while Toby was having some success, Kate was struggling despite changing her diet.

Despite the fact that her work contract essentially dictates that Metz needs to shed pounds for her role, the actress said that weight loss is a choice that she wanted to make for herself.

"Whether or not I lose weight or stay the same, it's purely a choice of mine for health," she clarified. "Not because I think that plus-size, curvy, voluptuous, big bodies aren't attractive — because I think they're awesome and sexy," she continued.

"So I'll just have to make sure that's known," she added, "because I'm not selling out the big girls. I don't do that. That's not me."

"This Is Us" season 1 airs Tuesdays at 9 p.m. EST on NBC.