Heh, when my older boy was six he was upstairs playing on the computer. His mom heads up with a snack for him, and her footsteps are greeted by a franctic "Don't come up, don't come up!"
Which of course any mom knows means she'd better just get on up there.
The poor lad had typed "sex.com" into the browser, a predictably eye-popping experience, and tried to close the window when he heard her coming. Of course this just generated an endless sequence of porn-site popups that got bigger every time he tried to close one...