From “The Best Motion Picture Interview Ever Written”, by Theodore Dreiser, Photoplay Magazine, Vol. 34, No. 3, August, 1928, pp. 32-35, 124-129.
[Novelist Theodore Dreiser interviews the Master of Comedy Mack Sennett]
… One of the things I was moved to ask at this point was, slapstick being what it is, was there any limit to the forms or manifestations of this humor? And to my surprise, yes there was, and is.
“No joke about a mother ever gets a laugh,” he insisted most dogmatically. “We’ve tried that, and we know. You can’t joke about a mother in even the lightest, mildest way. If you do, the audience sits there cold, and you get no hand. It may not be angry – we wouldn’t put in stuff about a mother that an audience could take offense at – but, on the other hand, it is not moved to laugh – doesn’t want to – and no laughs, no money. So mothers in that sense are out. You have to use them for sentiment or atmosphere in burlesque.”
“In other words, hats off to the American mother,” I said… “But not so with fathers…”
“Oh, fathers,” he said dryly. “No. You can do anything you want to with them. Father’s one of the best butts we have. You can do anything but kill him on the stage.”
“And as for the dear mother-in-law,” I interjected.
“Better yet. Best of all, unless it is an old maid.”
“No quarter for old maids, eh?”
“Not a cent. A free field and no favors where they’re concerned. You can do anything this side of torture and get a laugh.”
In silence I began to brood over the human or inhuman psychology of that, but got nowhere for want of time…