The 37-year-old actor decided to lend his voice to the animated film last year so his sons, James, 10, and Henry, four, could finally watch one of his movies, but admits they weren't huge fans.
Asked if they had seen any of his work, the Irish star told PEOPLE.com at the premiere of his new film, 'Winter's Tale,' in New York City on Tuesday (11.02.14): "Epic - [but] they didn't know it was me, so that was kind of a bummer. They seemed to think it was all right. I don't think it went to the top of their favourite list of cartoons, which is a bit disappointing."
But Colin is very proud of Henry and James, who has Angelman Syndrome, a rare genetic disorder that can impair speech, movement and balance.
He said: "[James] is an absolute stud. Every day, just breaking down boundaries. He's an amazing boy."
The actor previously credited his eldest son for inspiring him to check into rehab for drug and alcohol abuse in 2005.
He said: "Everything he's achieved in his life has come through the presence and the kind of will that is hard work. He's a lot to be inspired by."