Loud noises, open oven doors and other folderol.
I don’t think there’s a cook alive who hasn’t heard all the various myths about soufflées: that they’ll fall at the drop of the proverbial hat, with the vibration of door slam, a heavy footfall, even a shout. Even among the enlightened who’ve sworn off such primitive superstitions, myths persist about soufflées falling when their preparers take even the briefest peek at them through an open oven door. That one has sticking power because it’s backed by a sound scientific principle. Namely, that soufflées rise as a result of heat. Therefore a cool gust will cause it to fall. The odds of that happening as a result of a momentary gust from an open oven door are low, however in the event the soufflé’s rising was momentarily interrupted, it would simply keep going once it heated back up again. So let your children play, my friends. Let them blow their little horns and bang their little toy drums. Your cheesy poof will be none the worse for wear.