Have any of your friends been acting strangely? Perhaps they are aliens from another planet.
Follow the tips below and you will reveal an alien's identity before he or she can do anything bad to our beautiful planet.
Experts say that when an alien is extremely angry, he or she will speak in their mother tongue. So, annoy the suspect until he explodes and see if he uses a language you have never heard.
Ask him to breathe into a bottle of lime water and see if he is unusually reluctant to do so.
Take him to an astronomy lecture and see whether his eyes glow with extraordinary excitement at the sight of photos of galaxies.
Get a device which can generate sounds of different frequencies. Turn it to a sound level which humans cannot hear and then turn it to the highest sound level. Note his response.