User blog comment:The Koromo/WTF/@comment-25428589-20150704170536

What page was that on?

When I was a semi-active editor on Wikipedia, I saw this happen a couple of times (probably the most interesting of which being when someone made the entire page for UK politics display an image of Ed Milliband covering all the buttons, menus, etc).

IIRC, it's just a clever use of divs by vandals, with the z-index set very high and the width and height set to 100%.