1. Nobody knows who built the Taj Mahal. The names of the architects, masons, and designers that have come down to us have all proved to be latter-day inventions, and there is no evidence to indicate who the real creators were. 

2. Clans of long ago that wanted to get rid of unwanted people without killing them used to burn their houses down -- hence the expression "to get fired"

3. Minus 40 degrees Celsius is exactly the same as minus 40 degrees Fahrenheit. 

4. Cats can hear ultrasound. 

5. The metal band that connects the pencil eraser to the end of the pencil is called a Ferrule.