Partridge first appeared on BBC Radio 4's On the Hour twenty years ago, followed by BBC Two comedy show The Day Today. Coogan admitted to finding the fictional broadcaster's early television appearances "crude", while Iannucci explained that the character has evolved in a way which means he is now "more comfortable with himself".
Speaking at a Sky Atlantic press event for Alan Partridge: Welcome to the Places of My Life, Coogan said: "The fictional character Alan has not changed at all. But the way we write him has.
"I watched some of the early stuff recently from The Day Today for a montage and his voice was different. The voice started a bit like John Motson and has become more and more like me. It's a little bit more unrefined."
Coogan said that he believes recent series Mid Morning Matters is among "the best [work] we've done" on the character and that Partridge is now "more nuanced", adding: "I think it's a lot more subtle... I actually thought some of the Day Today stuff was quite crude looking back. I think some of the things we found funny, wouldn't pass for muster now."
Iannucci observed: "I think Alan has changed slightly over 20 years. I think he is far more comfortable with himself and he likes surrounding himself with young people now."
Coogan also described Partridge's original incarnation as "right-wing and intolerable" during the press call, but said that he thinks the character is now funnier as he is "trying to be liberal and [is] trying to move with the times".
Alan Partridge: Welcome to the Places of My Life airs on Monday, June 25 on Sky Atlantic.
Watch a classic Alan Partridge clip below (note: video contains strong language and adult humour):