Veteran actor Michael O'Neill has heroically saved world leaders on 24 and The West Wing (and played CIA and FBI agents in several other projects), been a gun-toting, grief-stricken widower on Grey's Anatomy, and, in 2014 alone, played a drug lord on Bates Motel, an ambitious senator on Rectify, and the mysterious, perhaps not-well-intentioned boss of Halle Berry's astronaut on CBS's Steven Spielberg-produced summer drama Extant.

The Alabama native, who splits his time between Los Angeles and his home state, is a thoughtful raconteur when it comes to sharing memories of his TV roles. On this, the occasion of adding his 100th credit to his résumé, courtesy of the Extant gig ("I was shocked that it would be such a delicious credit," he says), O'Neill takes a walk down memory lane with Yahoo TV.

The West Wing (1999-2006)

"One of the guys who had coached me in high school football, or junior high school football, was a cousin to Jerry Parr, the Secret Service agent who pushed Reagan into the car after the Hinkley assassination attempt. He saved his life. He got him to George Washington University Hospital. Jerry Parr was kind enough to share with me all of the behavior that transpired in that event, which Ron Butterfield used [when President Bartlet was shot], from the way that I searched for the wound when [Bartlet] pulled away ... he was arguing because he wanted to go get to his daughter, which I completely understood. But I was like, 'Mister President, this is not a conversation we can have.' He turned and looked at me, and there's a little drop of blood in the corner of his mouth, and it was oxygenated, it had bubbles in it, so I knew it was a lung. Jerry Parr gave me all of that. It just was one of those things that, as an actor, you're like, 'Oh, my God. This is not theory to him, this is not practice to him, this is his experience.' He couldn't have been nicer about it or more patient with me about it, because I had a million questions. Then I passed his number along to Aaron Sorkin, who I know had a conversation with him. It's one of my favorite things that I've ever done, getting to do that with Martin [Sheen], but really based on Jerry's life. It gives me chills to think about it. It's just so compelling to me — the sacrifice, and the intelligence those guys have. They're my heroes."

24 (2001)

"I did get to help start it, didn't I? It was fun, because I got to start [Jack Bauer] off, to confide in him that there was going to be an assassination attempt against President Palmer, that there was no telling what it would do to the nation, and that I needed him to stop it. I was also one of the first guys killed for my trouble, but he obviously did a good job, because Palmer lived. I knew what I was doing."

[Related: '24: Live Another Day' Finale Director on What That Shocking Silent Clock Means for Jack Bauer]

Grey's Anatomy (2010)

"Gary Clark… I didn't know if it would resonate or not, but all of us, I think every one of us, has some spot in us where we would kill to protect someone. That, at the end of the day, was what happened with Gary Clark. His wife was what he would kill to protect. Once he became untethered and had no one, what he did was seek out revenge against someone who took the thing that he valued most in this life. He felt he didn't protect her. He wasn't there to save her. He couldn't convince them.

[Related: Isaiah Washington's 'Grey's Anatomy' Return: Burke Came Back, But Was It Worth It?]

"That role changed my career. It was probably the hardest job I've ever done, hardest work I've ever done. I had a tremendous resistance to it, and I almost turned the role down. I was so afraid of that being sensationalized, and I didn't want that in the world. I hadn't worked with Shonda [Rhimes], and so I didn't know. I certainly knew she was a brilliant writer, but I didn't know what the intent was. We had a conversation about it. I said, 'You know what? Can I think about this and call you back tomorrow?' I called her back, and I said, 'Shonda, I just have to say it frightens me. It really frightens me.' She said, 'Michael, it frightens me too.' I thought, OK, we're at least starting at the same place. Her writing was so good. ... We saw the wound. We got to see the wound that drove him mad, and I think that was terribly important. It was important to show the fracture that brought this man to that desperate action."

Bates Motel (2014)

"They warned me when they brought me on board that I was only going to go one season with them. Hopefully I left them wanting more and not wanting less. It's a complicated family. Nick Ford was a complicated character, as most self-made men are. He's a man that kept a foot in both worlds, and it made him remarkably dangerous. Ford was a very successful businessman. He was able to legitimize himself. But he also never lost his ability to pick up a hammer. His downfall was he just didn't use the hammer quickly enough.

[Related: 'Bates Motel' Producer on Norman's Blackouts, Those Awkward Mother-Son Moments, and What to Expect in Season 3]

"I got to work with Vera Farmiga once before. I did a little film with her called Nothing But the Truth. I only had a brief experience, but I thought to myself, 'I hope I get to work with this actress again, because she's so alive.' There was something about Vera, about Norma, that was so disarming to Nick. She was making a pact with the devil without realizing that I was the devil. I was, at the same time, flirting with her a little bit. Not Michael to Vera, but Nick to Norma. It certainly left vulnerability. Nick Ford didn't get where he was by misreading people very often. He did her."

Rectify (2013-present)

"Senator Roland Foulkes is a man, I say of him, he's a man of great appetites. He wants what he wants when he wants it. He's certainly a political animal. My character's at odds with Daniel being out of prison. I have designs on continuing to feather my political résumé. It's a hindering spot that a man that I made my political bones prosecuting, that his sentence has been vacated. There's a real conflict between us, and I think we learn a great deal more about Foulkes in Season 2.

[Related: 5 Reasons Why You Need to Start Watching 'Rectify']

"When Ray McKinnon created this, he understood something about the rhythm of the South. I'm a Southerner, so to have a wonderful Southern story that's true to our rhythms being reeled out the way that Ray has done, this is really compelling. He's been a warrior to make sure those rhythms are true and that those characters are true to the backgrounds we come from. He knows that world incredibly well. I think that's been very, very satisfying to see something about the South that has its tentacles and veracity."

Extant (2014-present)

"In terms of Alan Sparks, they've just given us the tip of the iceberg. You don't get to a position like that, running an international space agency, without being a mission-driven person. He's the only holdover from NASA, when space exploration was a public enterprise. Now it's moved into a private enterprise. Sparks had actually flown and commanded a mission to Mars that we lost [while] landing, but he was able to get his crew and his vessel back against rather extreme odds. He's a man that's very willing to deal in crisis and very willing to lead. He's really mission oriented. There's kind of a singularity of focus when he gets into that that makes him… determined, I would say. Somewhat myopic. We end up with this extraordinary event that occurs with Halle on the 13-month solo mission, as she comes back after this encounter and finds out she's pregnant against all sane odds and explanation. Sparks gets involved… actually, has been involved all along, but gets involved in a way that hopefully will move the story in a surprising way. Forgive me, because there's only so much I can say at this point.

[Related: Which 'Real World' Alum Did Halle Berry Choose to Play Her Best Friend on 'Extant'?]

"But I can tell you there's a great deal more to Sparks, both on the good and the dangerous side, than has been revealed to date. He cares about his astronauts a lot. There's such trust among that core group of people, because they're so dependent upon one another. Yet, the nature of this event… when something so profound occurs, which has the potential to change the planet, you fall on one side or the other about how to relate to that. Sometimes that puts Sparks in complement to them, and sometimes it puts him in conflict."

Extant airs Wednesdays at 9 p.m. on CBS; Rectify airs Thursdays at 9 p.m. on SundanceTV.