What famous film is based on a true story without anyone knowing because it would be humiliating?

 The Dinner of Cons by Francis Veber is inspired by a true story…

The concept of the “idiot dinner” was invented by the surrealist André Breton in the 1920s. The guest who managed to bring the biggest idiot with him received congratulations from his friends.

This concept was then taken up in the 1980s by Jean Castel, boss of the eponymous private club in Saint-Germain des-Près.

Jean Castel

Only a small circle of show biz insiders knew about it.

One of the regulars at these dinners was the host Jacques Martin.

It was also through the latter that Francis Veber learned of the existence of this nasty entertainment.

The scenario of Le Dîner de cons is largely inspired by real anecdotes provided to Francis Veber by Jacques Martin.
For example, the day before a dinner for idiots, the pigeon that the host of Antenne 2 was supposed to bring had failed him, and he had to find another one in a hurry.

Jean Castel then advised him to invite a famous French director, whose name has remained secret to this day...

The actor Claude Brasseur was also invited to a dinner for idiots at Castel. But on the idiot side.

At the time, he was doing the Paris-Dakar and he was obsessed with racing. All he had to do was plug it in and he could talk about it for hours.

A clearly stupid and stupid subject for the audience at Castel's dinners.

Source:

Vanity Fair - Article by Pierrick Geais (April 2018)