"It was incredible!" Smollett said. "She landed at 1 a.m. She came into the studio. We were there until seven in the morning, and we just recorded the song, and it was incredible, and I love her. It's different getting to know someone that you love and respect and being able to work and do the work with that someone."
As a child of the '90s, Smollett grew up idolizing his generation's biggest vocalists, like Carey, Whitney Houston, and Celine Dion.
"To be able to sing with any one of these incredible women just... it makes no sense," Smollett said.
After working together, Smollett joked that now he and Carey "go back like babies and pacifiers" -- a reference to a line from Ol' Dirty Bastard's remix of Carey's "Fantasy." Not only was Smollett's collaboration with Carey a dream come true for him, it also scored the 33-year-old actor some cool points with his little brothers when Carey called him on his cell phone.
"She called and it said 'Mariah' and my brothers look at me like, 'Word?'" Smollett recalled. "Then I picked it up and she's like, 'Darling!' and they are like [gasp]."
In her guest role, Carey will play Kitty, a superstar who comes to Empire to collaborate with Jamal on an explosive new song. Carey told ET that the character will be "pretty glamorous," but will have more layers to offer.