Aliens steal our water. The universe is experiencing a drought, and Earth is the last place left where you can simply turn on a tap and drink. Aliens bring those large water-cooler jugs and take their fill, never returning the favor.
Aliens eat cats. Cats are a delicacy on alien planets.
Aliens eat name-brand candy. Sprinkle pieces in the forest and little aliens come scurrying out for more.
Aliens never got their flu shots. Sneeze in their face (or the closest approximation) and they’re down for the count. Weaklings!
Aliens either have tentacles, long limbs, or tubes coming out of their bodies. Some kind of long, gangly feature.
Some aliens have sharp teeth. Those are the biters.
Aliens have green blood, or come from a green planet, or use green light bulbs on their ships.
Some aliens have eyes like a squid, others have eyes like a shark. Most have brows that are permanently creased, making it look like they are deep in thought over how best to kill and devour you.
Aliens are flabbergasted by devices such as blenders, TVs, microwaves, and other common household appliances. This in spite of their far superior space flight technology.
Aliens can read our thoughts. This makes them hate us; they see we are just as petty and mean as they are.
They also hate us because we are free.
Aliens are like ants or bees. You have to kill the queen or else they’ll just keep on coming.
Aliens can learn English much more easily than we can learn their language. They like to hold that over our heads, as if bilingualism is a measure of intellect.
Aliens have very good poker faces. An alien’s face is located on the inside of its abdomen or under its left tentacle, making it difficult to see.
Aliens care not for trivialities such as precious metals or paper money. They want plastic bags and pandas. We’re not sure why.
Aliens love to conquer but have no plans for post-war infrastructure. They just say Mission Accomplished and call it a day.
Aliens saw Ingrid Bergman on TV and would like to know if she’s available for coffee sometime. Strike that — anytime.
Parasitic aliens are covered in slime.
Don’t lend your car to an alien. It will ruin the transmission, rip out the passenger seat, then do donuts in an empty parking lot. This after killing and devouring you.
Aliens will steal all your good ideas and never return your calls when they get famous.
Aliens love mayonnaise.
Aliens cannot grow facial hair.
Do not confuse aliens with intergalactic robots. Aliens will kill and devour you, while robots talk in mechanical voices. There are other differences, but that’s another list.