Most people in a  custard pie fight in a film
Who
Stan Laurel, Oliver Hardy
Where
United States ()
When
1927

The largest number of pies thrown in a custard pie sequence in a movie was 3,000 in the Laurel and Hardy silent two-reeler <em>The Battle of the Century</em> (USA 1927).  The director, Hal Roach (USA) bought the entire day's stock from the Los Angeles Pie Company.