EXCLUSIVE: 'This Is Us' Cast Talks Guest Sylvester Stallone, the 'Huge Hint' About Jack's Death in Season 2

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Though it’s easy to fangirl/boy over the Pearson family, the cast of This Is Us recently had a star struck moment themselves when Sylvester Stallone visited the set for a guest appearance.

WATCH: Sylvester Stallone Kicks Off Filming 'This Is Us' With Milo Ventimiglia, Chrissy Metz and Justin Hartley: Pics!

“He’s very congenial,” Chrissy Metz told ET’s Leanne Aguilera of the 71-year-old action star at the For Your Consideration panel on Monday. “He came in the makeup trailer, and he’s talking, he’s making jokes and he basically knows [co-star] Chris [Sullivan]'s entire resume. It was so cute… He knows people’s names, and he just cares and that’s super cool ‘cause he's a busy guy.”

Metz, 36, also opened up about her epic photo in which she’s punching Rocky himself, insisting, “It was all his idea ‘cause I would never be so presumptuous. But he could not be more lovely. It was so fun.”

Her co-star Milo Ventimiglia had previously worked with Stallone on Rocky Balboa, and relished the idea of a reunion.

“Being on set with him is one of the best career experiences I'd had in the past, so to be able to pick the phone up and be able to call him and say ‘Hey, would you like to be a part of this? We'd love to have you.’ And then for him to respond and be like, ‘Yeah I totally want to be there.’ It was great,” Ventimiglia said. “It was exciting, and he had a blast.”

But an A-list guest star won’t deter fans from season two’s biggest question – How did Jack Pearson die?

True to form, the cast remained tight-lipped on the subject, but did reveal that viewers won’t have to wait long to get the answers they’ve been desperate for all these months.

“You don't want to know,” Mandy Moore insisted when asked about the death of her on-screen husband, played by Ventimiglia. “Wait until Sept. 26th, and then there will be a giant hint as to what happens with Jack. There will be.”

MORE: Sterling K. Brown on Fears of 'This Is Us' Sophomore Slump and Secrecy Over Season 2 Premiere's Final Scene

Her co-star, Sterling K. Brown, added, “[There’s a] huge hint. As a matter of fact, in the last scene of the script it says, ‘Omitted for Secrecy.’ So, like, we know what it is, but he just didn't put it down in writing ‘cause he didn't want it to get leaked.”

For more from the This Is Us cast, watch the clip below!

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