What is considered the hardest riddle in the world?

It's Apparently Still a Riddle...

There seem to be various contenders for what is considered the hardest riddle in the world. Here are some brain-twisting responses from WikiAnswers contributors:

1)

• I turn polar bears white

  And I will make you cry.

  I make guys have to pee

  And girls comb their hair.

  I make celebrities look stupid

  And normal people look like celebrities.

  I turn pancakes brown

  And make your champagne bubble.

  If you squeeze me, I'll pop.

  If you look at me, you'll pop.

• Can you answer this riddle? - 97% of Harvard graduates couldn't answer this, but 84% of kindergarten students could (in less than 6 minutes).

Answer: The answer is "pressure," although some people have argued that the answer is "time" because it refers to the following poem. The simple answer is either Yes or No, because that is what the question literally asks, and kids would give up sooner.

Time

The time has come,

winter is here

and those yellow bears disappear.

The time has past

as man looks back with a sigh

and a tear in his eye.

As time is held

boys cross their legs

but of course the toilet begs

As time marches on

Girls loose their blush

and swap a comb for their brush

As time passes

For those held high

their end is nigh

As time catches up

Everyone is equal

when we get to the final sequel

As time turns

Without it we have flour and water

With it we have breakfast for my daughter

As time revolves

into something so fine

As time runs out

The more in a minute you try and squeeze

the less you can do with ease.

As time ticks

All the time that has past

man cannot comprehend something so vast.

(See Related question.)

2) The Chicken Riddle

If a chicken says, "All Chickens are liars" is the chicken telling the truth?

Answer: Chickens can't talk!

3) Village of Truths/Village of Lies

A man is traveling to a town and comes to a fork in the road. If he goes left, he goes to the liars' village. If he goes right, he then goes to the village of truths - which is where he wants to go. However, he does not know which way is which.

He doesn't have time to go both routes, so he approaches a stranger who is standing in the middle of the fork. The stranger says he may only ask 3 questions and he will answer them.

The man asks, "Are you from the village of truths?" The stranger says, "Yes!" However, the man is still facing a dilemma: If the stranger was from the village of truths he can only tell the truth, but if he was from the village of liars, he would say he was from the village of truth.

So then he asks the stranger, "Are you telling the truth?" The stranger says, "Yes!" But sadly this leaves the man in the same position as before.

Can you figure it out ?

Answer: The man finally realizes that what he must do is ask the stranger the path back to his own village. If he was from village of truths, he takes him there. Even if he is from the village of liars, he will still take him to the village of truths.

4) What am I ?

If you look you cannot see me. And if you see me you cannot see anything else. I can make anything you want happen, but later everything goes back to normal. What am I?

Answer: Your imagination