But the actor and comedian was not afraid to open up with ET exclusively on the set of Brooklyn Nine-Nine where he was filming an upcoming guest spot. For the first time, he goes on the record about covering up that giant "Mariah" tattoo and also talks about his former All That co-star Amanda Bynes.
Earlier this month, the America's Got Talenthost was spotted in Studio City, Calif., with a giant crucifix tattoo on his back, covering up the ink of estranged wife Mariah Carey, but Nick told ET's Kevin Frazier that there's more body art to come.
"When it's done, I'll show up to your house naked and I'm going to let you see all the work," the 34-year-old joked with Kevin. "I'm not even half way done with it. That's what kind of made me mad, because everybody was like, 'He's showing off his tattoo!' ... Trust me, when it's done, y'all ain't going to be able to pay me to keep my shirt on. Right now, it's not finished."
Nick and Mariah married in 2008 after a whirlwind romance, and have two children together -- twins Moroccan and Monroe, 3. In August, Nick revealed that he and Mariah had been living in separate houses for months.
"It defintely gets hard a times," said Nick. "You want to say certain things or lash out. Sometimes public opinion wants to paint you a certain way. At the end of the day that's not what it's about. Ultimately, I want to do what's best for my family and for my children."
While Nick wades through his life trials, fellow former Nickelodeon darling Amanda Bynes continues to make headlines. The actress is currently on psychiatric hold after displaying erratic and bizarre behavior, which included making allegations that her father abused her. She later took back the allegations, denying that there was any truth to them.
Having worked alongside Amanda over a decade ago, he has always been very candid about his thoughts on her troubles.
"I've seen it before and it's sad, because I've known her since she was a child and I just see somebody crying out for help more than anything," said Nick. "I've always reached out to her and let her know I understand and we can talk about it. She was welcoming to that. Right now it's just one of those things where all we can do is pray for her and hope that she continues to get help and stay focused within that help. If she dedicates her time, she'll definitely be better."