ET caught up actor Ryan Eggold at the Mike and the Mad Dog Reunion Show at Radio City Music Hall on Wednesday night, where he confirmed reports that X-Men actress Famke Janssen is joining the cast.
"We're introducing a new character," Eggold tells ET exclusively. "Famke Janssen is joining the show and I just met her and she's amazing."
"All I can say is there's a ginormous, massive event coming that I'm just really curious to see how everybody reacts to," he adds. "It's a big attention shift, and it changes everything about the show."
NBC is currently planning a Blacklist spinoff with 51-year-old Janssen as the lead, according to Variety. Janssen's character -- Susan "Scottie" Halsted -- is rumored to be the mother of Eggold's character Tom. However, the 31-year-old actor couldn't give away too much.
"Well, I can say potentially if that ever happened, it would be exciting," he says. "There's so much we can do with this character in terms of him being an agent that takes on different masks, and different characters, and infiltrates different kinds of places. If it ever did happen, it would have a big effect, but I can't say."
Eggold has nothing but praise for Janssen, whom he calls "sweet and beautiful."
"She's stunning as a woman and as an actress, and I’ve thought that for years, as many of us have," he gushes. "This part required somebody great and she was just at the top of the list and one of our first thoughts. She's just the woman made for the role. She's just perfect."
"She's so sweet and beautiful in every way but mysterious," he continues. "She's got a lot of things that make her really right for the character."
All proceeds from the Mike and the Mad Dog Reunion Show on Wednesday night benefited the Garden of Dreams Foundation, a non-profit organization that works to positively impact the lives of children facing obstacles.