Answer:
You have a bucket full with 5 gallons of water. What can you ADD to it in order to make it 3 gallons?
What always comes into a house through the keyhole?
What goes up the hill and down the hill, And spite of all, yet stand still?
An archaeologist unearths a coin bearing the inscription "57BC". How does he instantly know that it's a forgery?
The yellow house has yellow window, the red house has red windows, what colour windows does the green house have?
It is something you will never see again.