So it was no surprise that while filming Cops L.A.C. on location, locals thought he was the real thing.
"We did Coogee Beach the other day and we had a couple of kids who saw the police uniform and crowded people on the beach, and they walked up and said to me, 'Mate did someone die?'" he explained.
"I said, 'No, no, no! We’re shooting a new police series' and they said 'Ohhh' and walked away."
O'Sullivan is no stranger to police roles. His character of Senior Constable Nathan Holt is the fourth time he has played a cop.
"I've done a lot of scenes with Roy Billing and working with an actor of his experience I learned a hell of a lot and just seeing the way that he goes about his work has been really great," he says.
He's also keen to muck in with some of the stunts involved with the show's action scenes.
"I had the opportunity to do a lot more than I actually thought, which is great. Early on there were a couple of stunts and they have been continuing through the series.
"I won’t say which ones I don’t do, but I really enjoy it and I feel sort of weirdly obliged to stick my hand up and say 'Yeah I’ll do it, no matter what'."
So far Nine's newest drama is still carving out its audience, competing in a genre crowded with competition, including TEN's Rush in the same time slot. Its premiere pulled a healthy 1.16 million viewers. This week it had dropped to 712,000.
O'Sullivan isn't sure when cast may get the word on a possible renewal. As any actor knows, it helps to be realistic about the future of a show in TV's numbers games.
"I think by the end of the year we will certainly know. Hopefully before then as we're wrapping up the first season. Everyone is very hopeful. It would be great to see how the characters develop through the series. Everyone seems to hit their straps about halfway through, it would be great to get the chance to go again."
Cops L.A.C. airs 8:30pm Thursdays on Nine.