Well, on our city's main website, if you want to apply for something online, on april fools, you had to think what the hell you should do.
First of all, all online webforms were mirroroed, which looked pretty damn cool actually.
Second of all, you can reverse it easily, by clicking the reverse button, that's spelled in reverse as well as mirrored.
It's also been half transparent.
On the other hand clicking it was no small feat because mouse movement had been flipped upside down and mirrored, and the reverse button was moving around.
Can you imagine how many people got irritated ?
No one however noticed that the simplest way of putting it back to normal was to simply refresh the site
The laughs we had at work for this is priceless