Farrell, 35, said at Comic-Con his career had some bumps early on, not the least of which was too much partying, which led to his decision to jump on the wagon.
"Success came really quickly for me. It was insane," said Farrell. "Recently I reconnected to that Colin who went to his first acting class in Dublin at 17."
Farrell appeared at the convention for comics, science fiction-fantasy and pop culture to talk about his role as Jerry the vampire in "Fright Night 3D."
The Los Angeles Times said Saturday that Jerry apparently was in the right vein even though this particular vampire is no "Twilight" heartthrob. "It (the script) was so clearly written for me, I could visualize it instantly," he said.
"Fright Night 3D," a remake of the 1985 release starring Chris Sarandon, opens Aug. 19.