The pair co-starred in the hit show from 2007 to 2010 and have recently reunited to film the Christmas special.
But now Rob Brydon has praised James Corden for not turning "into an arse" after finding fame in the US, as he said he feels "paternal" towards his Gavin And Stacey co-star.
Since the show started, Corden has enjoyed success as a talk show host in America.
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But asked if he had changed for the worse, Brydon told The Sunday Times: "Oh no, no, no... James has certainly not turned into an a***.
"I would say the opposite.
"When we were shooting Gavin And Stacey, I thought, this is going to be interesting. It's 10 years since we did the show. And James, could he be any more successful? I don't think he could.
"And I'm not just saying this because he's a friend, I thought he was a fantastic example of how to behave when you have that status and position.
"I came home and said to (wife) Clare, 'James was just...' I thought he was just text book."
The star, 54, said he feels paternal towards Corden.
"I don't think he gets enough credit for what he's done," he said.
"He can write, sing, dance, act, present.
"Did you see him when he hosted the Tonys? I couldn't learn that if you gave me a year. Well, maybe a year. People don't stop and think how terrifying that must be.
"I'm possibly his biggest fan."
Brydon and his wife visited Corden, 41, in California this year.
He said: "When we left, Clare said to me, 'Golly, you really are very paternal with James, aren't you?' And I feel that way. I'm so proud of him."