The Ice Age star was honoured with a Doctor of Fine Arts from Emerson College in his native Boston, Massachusetts and recently returned to the school for his son's graduation.
His title allowed him special privileges, which annoyed scholars.
He tells WENN, "My son just graduated with a degree in filmmaking, and a guy looked down his nose at me because they had doctorates in a special seating area and I was going in there. This guy, who was a real academic - like a real doctor with letters, turned around and said, 'Excuse me but this is for doctors only,' and I'm like, 'Yeah, I'm Dr. Denis Leary!'
"There I was sitting right next to him at the graduation with all the other f**king doctors! He was not happy.
"I used to think the doctorate honour was really bulls**t, but now that I have a doctorate I think it's a really smart system. (Comedian) Bill Cosby actually got his real doctorate by going back to school. He must be p**sed! I'm Dr. Denis Leary, he's Dr. Cosby. It's cool to be able to say it."