Many Americans work side by side with space aliens who look human - but you can spot these visitors by looking for certain tip-offs, say experts.
They listed 10 signs to watch for:
1. Odd or mismatched clothes. "Often space aliens don't fully understand the different styles, so they wear combinations that are in bad taste, such as checked pants with a striped shirt or a tuxedo jacket with blue jeans or sneakers," noted Brad Steiger, a renowned UFO investigator and author.
2. Strange diet or unusual eating habits. Space aliens might eat French fires with a spoon or gobble down large amounts of pills, the experts say.
3. Bizarre sense of humor. Space aliens who don't understand earthly humor may laugh during a serious company training film or tell jokes that no one understands, said Steiger.
4. Takes frequent sick days. A space alien might need extra time off to "rejuvenate its energy," said Dr. Thomas Easton, a theoretical biologist and futurist.
5. Keeps a written or tape recorded diary. "Aliens are constantly gathering information." said Steiger.
6. Misuses everyday items. "A space alien may use correction fluid to paint its nails," said Steiger.
7. Constant questioning about customs of co-workers. Space aliens who are trying to learn about earth culture might ask questions that seem stupid, Easton said.
"For example, a co-worker may ask why so many Americans picnic on the Fourth of July," noted Steiger.
8. Secretive about personal life-style and home. "An alien won't discuss domestic details or talk about what it does at night or on weekends," said Steiger.
9. Frequently talks to himself. "An alien may not be used to speaking as we do, so an alien may practice speaking," Steiger noted.
10. Displays a change of mood or physical reaction when near certain high-tech hardware. "An alien may experience a mood change when a microwave oven is turned on," said Steiger. The experts pointed out that a co-worker would have to display most if not all of these traits before you can positively identify him as a space alien.