Now, he's turning to comedy, playing a NASCAR driver who helps Will Ferrell's character win every race in "Talladega Nights: The Ballad of Ricky Bobby."
On The Early Show Thursday, Reilly admitted he's finally making a name for himself, after years as a versatile character actor.
He said, after doing many films in a relatively short span, moviegoers are coming to recognize him on the street "more and more.
"People recognize my characters, is what it is," he told co-anchor Hannah Storm. " Not so much me, which is the way I like it. I like people to be surprised by what I do each time in a movie, instead of thinking they know my personality and they've come to expect something from me each time. I just want them to expect excellence, you know. Not necessarily any kind of certain personality traits or whatever."
As for the comedic role, Reilly remarked that he tries "to put as much variety in the things I do as possible. I feel like I've done comedy before, in more serious movies; funny parts in serious movies. I don't know. I'm just taking it as it comes. I'm not really making any big decisions in terms of like I'm never doing drama again. Just taking what they're offering right now."
Reilly said there was lots of improvisation as "Talladega Nights" was being made.
"Will Ferrell (who wrote and starred in the movie) and Adam McKay, the director, wrote a great script. So we did have an amazing script. But they also were nice enough to let us go crazy within the scenes."
Reilly remarked that he And Ferrell play well off each other because, "We have a real affection for each other. Will and I have known each other about six years now. We hit it off as soon as we met and I thought, 'I've gotta work with this guy someday.' I don't know, we shared something in common, a sense of humor, or something. I don't know."
Was he afraid he was taking the impromptu lines too far?
"At first, when I started out, I'm like, 'Yeah, it's kind of a new world for me playing this large of a part in a big comedy.' So, I would say to Adam, 'Am I going too far?' He was like, 'John, you can never go too far when you're doing a comedy like this. We can always pull it back in the editing, but it would be a shame if we didn't go far enough.' "
Several of the actors got to go to the Charlotte Motor Speedway for training in driving racecars. Reilly says he went 144 mph after a mere 20 minute orientation.
He admitted he was "terrified," adding, "I wasn't even paying attention to how fast -- they don't have a speedometer on the car."
What was the adjustment like when he got back onto regular roads?
"Once you get to 150 or 144, whatever it was, 70 feels like, you know, the slow lane all of a sudden!"