There are are five things wrong with this sentence; only geniuses will be able to to spot all of the mitstakes

Two guards were on duty outside a barracks. One faced up the road to watch for anyone approaching from the North. The other looked down the road to see if anyone approached from the South. Suddenly one of them said to the other, "Why are you smiling?"

How did he know his companion was smiling?

Can you decipher the following common phrase?

T M C
A U O
H S M
W T E

I have a five and a three-gallon jar. Assuming there is an infinite supply of water, how can I measure one-gallon water?

What has no start, end, or centre?

A man is found unconscious in front of a store at two in the morning. His head is bleeding and there’s a brick laying next to him. When the police arrive, they carry the man to jail. Why did they arrest him?

I am the fastest animal but cannot climb the tree. What am I?

What can run but never walks, has a mouth but never talks, has a head but never weeps, has a bed but never sleeps?

Can you calculate the probability of getting a sum of six when a dice is thrown twice?

Rearrange the letters in "new door" to make one word.