The Kelly-Hopkinsville encounter

The Kelly-Hopkinsville encounter, also known as the Hopkin Green Men case, is an alleged close encounter with supposed aliens and one of the most well-known and well-documented cases in the history of UFO incidents, and a favourite for study in ufology. The incidents began on the evening of August 21, 1955 and continued through to the dawn of the next morning. The incident occurred mostly around a rural farmhouse at the time belonging to the Sutton family, which was located near the small town of Kelly and the small city of Hopkinsville, both in Christian County, Kentucky, United States. Witnesses include policemen and state troopers, and the incidents were taken seriously enough as to be officially investigated by the United States Air Force.

There were dozens of eyewitnesses to the incidents, which included two families present at the farmhouse and others in the area, including policemen and a state trooper who saw strange phenomena such as unexplained lights in the night sky and noises the same night. The seven people present in the farmhouse would claim that they were terrorized by an unknown number of creatures similar to gremlins, which have since often been referred to as the "Hopkinsville Goblins" in popular culture. The residents of the farmhouse described them as around three feet tall, with upright pointed ears, thin limbs (their legs were said to be almost in a state of atrophy), long arms and claw-like hands or talons. The creatures were either silvery in color, or wearing something metallic. Their movements on occasion seemed to defy gravity with them floating above the ground and appearing in high up places, and they "walked" with a swaying motion as through wading through water. Although the creatures never entered the house, they would pop up at windows and at the doorway, working up the children in the house to a hysterical frenzy. The families fled the farmhouse in the middle of the night to the local police station and sheriff Russell Greenwell noted they were visibly shaken. The familes returned to the farmhouse with Sheriff Greenwell and twenty officers, yet the occurances continued. Police saw evidence of the struggle and damage to the house, as well as themselves seeing strange lights and hearing noises. The witnesses additionally claimed to have used firearms to shoot at the creatures, with little or no effect, and the house and surrounding grounds were extensively damaged during the incident.

Even years later the eyewitness stories still collaborated remarkably under individual questioning, although speculation amongst the eyewitnesses regarding the motivations of the creatures has ranged from field study on their part, or that the creatures were acting out of mere curiousity or even outright malevolence. The two families involved were noted locally to not be the types to make up a hoax, and this would be seemingly backed up by the fact the families obtained no financial gain or significant fame from the incident, and fled the area when the incident became known locally and they gained an abundance of tresspassers wanting to see the site.

UFO researcher Allan Hendry wrote "[t]his case is distinguished by its duration and also by the number of witnesses involved." Jerome Clark writes that "[i]nvestigations by police, Air Force officers from nearby Fort Campbell, and civilian ufologists found no evidence of a hoax". Although they never formally investigated the case, Blue Book confessed to being stumped. So was Isabel Davis, one of the most hardheaded of UFO investigators.

Here is the wikipedia article where this information was taken from. A detailed account can also be found there.