Dermot Mulroney Admits It Was 'Satisfying' Punching Dylan McDermott After 30-Year 'Rivalry' (Exclusive)

After years of mix-ups over their similar names, the "rivals" finally face off for the first time on Tuesday's 'LA to Vegas' and ET has the scoop.

After decades of mix-ups over their similar names and looks, Dylan McDermott and Dermot Mulroney get to settle the score (finally!) on LA to Vegas.

On Tuesday's episode of Fox's rookie comedy, Mulroney guest stars as Captain Steve Jasser, a rival airplane pilot to McDermott's Captain Dave Pratman on Jackpot Airlines. When Dave is pulled away from his duties, Steve is called in to cover the quick Los Angeles-to-Las Vegas flight route. ET caught up with McDermott and Mulroney earlier this month to get the scoop on the anticipated small-screen team-up years in the making.

"Matter of fact, I get myself mixed up with him," McDermott confessed to ET's Leanne Aguilera at Fox's winter Television Critics Association red carpet. "We actually did an interview the other day, the two of us together, and I called him Dylan. So that's how bad it gets!"

The 56-year-old actor said it was "great" bringing his and Mulroney's real-life faux rivalry to TV "because we've been rivals for 30 years now," he quipped. "For him to come on and be Captain Steve and be the guy who does the international route and everybody loves him, and poor Captain Dave's in the shadows now was great."

McDermott revealed that it actually wasn't his idea to bring Mulroney on, but LA to Vegas creator Lon Zimmet who came up with the genius idea to have them share the screen for the first time. "He called me up and said, 'Would you mind Dermot coming on?" McDermott recalled. "I said, 'Are you kidding me? I would love that.'"

Mulroney spoke with ET's Katie Krause at the Hallmark Channel winter Television Critics Association red carpet on Saturday, where he dished some dirt about his one-episode guest stint. He adorably revealed that his heart was warmed after hearing that McDermott recently said at TCA that he now considered them to be "friends." "I was really touched, because we only recently made each other's acquaintance," Mulroney said with a smile. "I mean, the whole thing is ridiculous!"

It's no surprise that the two get into serious hijinks on LA to Vegas, with the two rivaling captains getting into fisticuffs. Asked what it felt like to punch McDermott in the face, Mulroney admitted it was quite fulfilling. "I would have to admit that somewhere deep inside it was somewhat satisfying," he said. "When great art and real life -- when they do mix and you as an actor can experience something cathartic like that -- it really sets off that experience. It was well worth the wait."

McDermott also recently shared a funny story about a moment in time when he seriously debated changing his name to "Mick Dermott" because of Mulroney. When ET revealed that fun fact to the 54-year-old actor, he couldn't help but laugh. Though he never thought about tweaking his name because of McDermott, Mulroney had this to say: "I've never even really wished that I had but I could have. The amount of time that I've spent explaining, discussing, spelling, pronouncing, apologizing for my name, I'd probably be about two years younger right now!"

LA to Vegas airs Tuesdays at 9 p.m. ET/PT on Fox.