Green Alien (Signs)

The Green Alien is the main antagonist of the 2002 science fiction-religious film Signs. It is a green skinned reptilian alien along with it's mysterious extraterriastial species it come froms, somewhat resembles the classic 'greys' of UFO lore.

History
Graham Hess is a former Episcopalian priest. His wife Colleen was killed in a traffic accident caused by Ray Reddy. The accident left Graham embittered and caused him to renounce his faith in God, and so left the ministry. Graham's younger brother Merrill, a former minor league baseball player, helps run the family farm and care for Graham's kids, Morgan and Bo. Bo has a habit of leaving half-filled glasses of water around the house, because "[they] taste funny".

Life at the farm is uneventful until a mysterious crop circle is found in the cornfield, but Graham thinks it's a hoax. That night, Bo wakes Graham up and says there's a monster outside. Graham tucks her back into bed, but then sees the silhouette of someone standing on the barn roof. Alarmed, he fetches Merrill and they try to scare away the figure, believing it's Lionel Pritchard, a local prankster. The brothers run screaming around the house to frighten off the intruder; it jumps from the roof and runs into the cornfield. Neither man get a good view of it.

The next day, Sheriff Paski stops by to investigate the incident. She admits that unless Graham has a clear description of the intruder, she is unable to help him. Their conversation is interrupted by Bo, saying that the TV is reporting numerous crop circles appearing in India. That night, the dog barks incessantly towards the cornfield. Taking a flashlight, Graham walks into the cornfield and yells that the intruders are "wasting [their] time." As Graham walks back to the house, he hears a noise and spots a thin green leg among the cornrows. He runs back to the house, terrified.

Later the family watches the television about reports of several unidentifiable and mysterious lights hovering over Mexico City. During a talk with Merrill, Graham dismisses his brother's belief in signs, evidence of some higher power, and says that they will have to face whatever it is alone. The following morning, Graham receives a cryptic phone call from Reddy, the man who killed his wife. Graham goes to see Reddy and finds him sitting in his car wearing a bloody shirt. Meanwhile, a frightened Merrill watches footage depicting an alien near a child's birthday party in Brazil. Reddy tells Graham that he is going to the lake, since none of the aliens have been seen near water. Before leaving, Reddy pauses to apologize for the accident that killed Colleen and tells Graham that he trapped an alien in his pantry. Investigating, Graham uses a kitchen knife to see the reflection of the alien under the door. A clawed hand reaches out and a startled Graham cuts off two of its fingers.

Back home, Graham gives his family the options to stay at the house or head towards the lake. They vote to stay, not wanting to leave their home. They board up the windows and doors, preparing for any possible attack. Meanwhile, it is reported that more mysterious lights have been spotted worldwide and that the aliens are hostile. Merrill suggests that the crop circles in their cornfield, among others, are for alien navigation.

Graham prepares a "last meal" for the family, with each picking their preferred dish. They are interrupted when they hear a baby monitor, which they had earlier discovered could pick up the aliens' communications, alerting them that the aliens are approaching. They listen as the aliens, seeking a way in, walk around the house. The dog, which was accidentally left outside, barks alarmingly but is quickly silenced. Merrill suddenly realizes that the attic was left unprotected and they quickly move to the basement, barring the door. The aliens can be heard inside the house and try to enter the basement. An alien grabs Morgan from the disused coal chute. It is driven away, but Morgan has an asthma attack. Graham realizes his inhaler was left upstairs, so he calms Morgan, hoping that the boy's breathing would return to normal.

The next morning, Morgan's condition has improved and the radio reports that aliens are retreating. They return upstairs but are ambushed by a lone alien, who takes the comatose Morgan hostage. Graham notices two fingers are missing, meaning it was the alien trapped in Reddy's pantry.Graham suddenly remembers the night that his wife died. She was pinned by a car and the Sheriff tells Graham that when the car is moved his wife will die. He talks to her and she tells him to let Morgan have fun and be silly, and for Bo to always listen to her brother because he will take care of her. She then tells Graham to "see" and "tell Merrill to swing away."

Graham realizes there was meaning in his wife's final words. Looking around, he sees Merrill's mounted record home run bat, next to Merrill. He tells Merrill to "swing away." Merrill understands and grabs the bat. Sensing an attack, the alien sprays a toxin into Morgan's face. Merrill swings at the alien, who then drops Morgan, causing one of Bo's water glasses to spill on it. The water acts like acid on the alien's skin, so Merrill starts smashing all of the half-filled glasses, before finally knocking the alien into a table, where water glasses spilled directly onto its face, killing it.

Characteristics
The aliens are comparable in height to humans, which can make them mistakable for being men under poor lighting conditions. Their skin has a reptilian green tint to it by default, which changes color to camouflage them with their surroundings. This attribute is so precise that it can even project facial features of others onto the skin. Their faces have general humanoid features, though they lack extruding ears and nostrils and feature milky, glass-like eyes. The aliens are also apparently carnivorous, with them featuring sharp white teeth. Protruding from their wrists are cones that dispense a gas that is toxic to humans. At maximum health, the aliens are extremely dangerous, with their strength and stamina being comparable to Olympic athletes in all regards. However, they are susceptible to water damage, which has an acidic effect to them.

While the characteristics of the aliens are largely speculative and inferred by the characters of Signs, it can be assumed that they are predominantly accurate. The aliens are implied to be master tacticians, with them recognizing the necessity of exploiting weaknesses of their prey, such as structural hindrances, etc. During invasions, the aliens mark their target locations with symbols that are used for coordination. The aliens' method of combat is hand-to-hand, as they recognize that humans have access to nuclear weapons, which would be impossible to content with.

Trivia

 * The aliens' intolerance for water was heavily criticized by fans and critics alike, due to Earth- the fictional species' target- having an atmosphere and surface predominantly made up of water.
 * A popular fan theory is that the aliens are actually demons, complementing the religious overtones of Signs. This theory is popular due to:
 * The aliens being intolerant to water handled by Bo, who is described by nurses as being like an "angel".
 * The CGI appearance of the aliens is inconsistent, which may be attributed to a unique interpretation to every character.
 * The aliens blend in with their environment and even show peoples' faces, representing inner demons.
 * When Graham faces an alien, he could be said to encounter his inner demon, which is is wife's death. Additionally, this confrontation brings him to grips with his face.