Yes, it was – but he did that self-deprecating/aggrandising thing of attributing his own joke to someone with higher cultural cachet by repeatedly claiming it was something George Bernard Shaw said about the theatre (though, it seems, Shaw didn’t). https://quoteinvestigator.com/2019/07/18/bladder/
Wasn’t it Hitchcock who said the length of a film should be based on the endurance of the human bladder?
Yes, it was – but he did that self-deprecating/aggrandising thing of attributing his own joke to someone with higher cultural cachet by repeatedly claiming it was something George Bernard Shaw said about the theatre (though, it seems, Shaw didn’t). https://quoteinvestigator.com/2019/07/18/bladder/