1. Global Warming
2. Diseases (Mad Cow, AIDS, SARS)
3. Nowhere to park (When was the last time you saw a UFO landing site?)
4. Water, Water everywhere and not a drop to drink
5. Too hot in the summer, too cold in the winter
6. Poor color choice (who made the Earth blue and green?)
7. Frightening creatures (Giant squids, Human beings, etc.)
8. Strange customs (Marriage for life, Ear piercing)
9. Mosquitoes (Aliens hate them too!)
10. Electricity (Most aliens have an electricity allergy)