According to hollywood.com, Grace, now 33, ran into a familiar face while on location in his hometown and he "relished the moment he got to boast about his star pals."
In an interview on "Anderson," which aired Tuesday, he said, "I bumped into someone -- no names mentioned, but you know who you are -- who was like a real bully to me at high school ... . It was the reason you wanna go into being an actor, go back and be like, `Hey, do you know Robert De Niro? Katherine Heigl?' It was great. I was a real jerk.
"(De Niro) had said, `Call me Bob,' which I had real trouble with because he's such a fantastic actor but when I saw my childhood bully I was able to say, `Hey, do you know Bob?'"
Grace has discussed his hometown in interviews; last year he revealed to Conan O'Brien he would shoot the movie in Fairfield County.
O'Brien told Grace it must be great to come home as a successful actor, but Grace joked about how his childhood bedroom still looks the same ("a bunk bed") and the bummer of having to spend the summer rooming with his parents.
"I really hope DeNiro comes over and visits you [there]," O'Brien said at the time. "Him in the bottom bunk."
Grace promised DeNiro "the top or the bottom bunk."