From a history of the Gilbert and Sullivan Savoy Operas.
The Mikado" had, of course, a very long original run. This engendered, eventually, a somewhat irresponsible attitude on the part of certain members of the cast.
Gilbert had made it his business to check up - and George Grossmith was not exempt from censure over his antics with Jessie Bond, who was playing Pitti-Sing. Gilbert had heard that in their scene with the Mikado, when kneeling before him, Jessie Bond had given Grossmith a push, and he had rolled right over.
Gilbert taxed the actor with this.
But I got a big laugh", protested Grossmith.
So you would if you sat on a pork pie", retorted the author.
"Pork Pie" laughs are laughs for the sake of laughs: laughs which - and this is why Gilbert opposed them - detract from the work as a whole.
Modern movies have an analogous problem with Pork Pie Peril - needless injections of arbitrary and artificial suspense and shocks.
For example, in Harry Potter and the Deathly Hallows Part 1, the three heroes are attacked by Death Eater villains during the course of a wedding celebration and just manage to escape by 'disapparating' (teleporting) into central London.
Then comes the Pork Pie Peril - the three heroes happen re-appear right in front of an on-coming double decker bus, and only just manage to get out of the way before being run-over.
These stupid injections are presumably taught in film school nowadays, since they are in almost every movie; including some of the best.
Directors must realize that Pork Pie Peril works like cheap laughs: they make movies worse, not better.