However, if you just go ahead and do it without asking, you can always apologize. As though you didn't entirely mean it.
Like when Miss C asks if she can pour a glass of milk onto the floor "just to see how fast it will flow." Versus doing it, looking surprised and saying, "Sorry! It was an accident."
Then getting irate with me, because that was her glass of milk, and here I am judging her intent.
She may have a strong career in advertising ahead of her.
Ralph Lauren last year apologized for this digitally altered photo which ran in Australia:
And then this one in Japan: