April Fool

It's that time of the year again and it's time for a prank. Tell us what pranks have ever occupied your day, so much that it made you annoyed for being troubled by it so much.

As for me, there was once upon a time, when I spent the whole day scratching my head, wondering why my laser mouse didn't work. Turns out it was something like this:

This is just a picture I found off the net, but it's similar.

I've also gotten these in the past years.
1) Why won't my soda open?

2) Door buzzer

3) There's a leek in the bathroom

And some others.

So what kind of pranks have you received or given to your friends and families so far?