The scene with the slowly deflating parrot on Peter Sellers' shoulder always sets me off. The sight of Clouseau with a floppy bird on his shoulder makes me laugh until I cry every time.

Some people chuckle most when the sleuth says "burm" or "minkey", or when he and manservant Cato get to grips in a martial arts confrontation. For me, it's the parrot every time.

So I missed five minutes of The Curious Case Of Inspector Clouseau as I mopped my eyes in the aftermath of a showing of that scene in this documentary, a dutiful account of how one of the big screen's most enduring comic characters was created.

It suffered from the absence of two key players. Sellers couldn't appear as he died in 1980, although footage of him talking about Clouseau was shown, and director Blake Edwards presumably chose not to appear.

The two didn't see eye to eye, going weeks without speaking to each other. They had different approaches to film-making - Sellers was a perfectionist, Edwards was slap happy - but both liked being the boss. They were, as one observer noted, "both men with tunnel vision, and saw themselves at the end of the tunnel".

Sellers was only supposed to be part of an ensemble cast in The Pink Panther before he and Clouseau effectively hijacked the movie from co-stars like David Niven. The British actor had not even been first choice. Peter Ustinov was originally slated to play the French policeman.

Sellers conceived Clouseau on the plane flying to Rome for filming. He took Clouseau's moustache from the photograph of the first man to swim the Channel and his trenchcoat from screen gumshoes like Bogart. A ludicrous accent, described as "English into which the deathwatch beetle of French has gone", completed the character.

Clouseau was such a hit that producers inserted him into the film of a country house stage thriller, A Shot In The Dark, for his second movie appearance. Ten years later, Sellers, who suffered a massive heart attack, and Edwards revived Clouseau out of mutual necessity to boost their careers.

If the Clouseau films became little more than Sellers in cabaret, doing slapstick comedy and adopting disguises, we shouldn't complain because they were always funny. So was Sellers. Asked what he was doing about his heart attacks, he replied: "I'm trying to give them up."

Movie-making has become a lot more marketing-conscious since Clouseau's time, as the final part of The Hollywood Machine showed. Nowadays, everything depends on the opening weekend box office results. Within 48 hours, makers know whether they have a hit or a turkey on their hands.

Almost as much is spent on marketing, as making a movie. Budgets of $50m to $100m to spend on worldwide promotions are common. The premiere and publicity junket for Pearl Harbour cost £5m.

There is, we were told, no such thing as a safe bet and that a winning formula remains a mystery. But I'd say that Sellers and Edwards, even if they weren't speaking, had found it with the Clouseau comedies.