People have told officers they have heard bangs next door and voices they cannot explain. One person called police in Mid Wales saying they thought a UFO had landed while another caller accused an individual of practising witchcraft.
One caller told police they believed there were aliens in their flat, while another claimed there were "loads of zombies around."
The unusual calls have been revealed following a Freedom of Information request. Twelve calls were recorded by Dyfed-Powys Police and one report was received by West Mercia Police. It's not unusual to see ghosts and witches on the streets this time of year.
Youngsters and their parents go door to door trick or treating, dressed up in outfits aimed to scare. It's the way it has always been at Halloween up and down the land.
But for some people, the scare factor is altogether more real – and it happens all year round. It's so real that they have called the police to report sightings of UFOs, aliens, and the walking dead.
The number of reports, as you might expect, is relatively low. But the descriptions provided by the public have ranged from one caller claiming there were aliens in their flat to another claiming their neighbour was indulging in witchcraft and sitting in their attic chanting.
It won't stop the majority of the people enjoying Halloween tonight – and hundreds are expected at Telford International centre throughout the day for drive-in screenings of films, culminating in the late night show of horror movie A Nightmare on Elm Street.
But for police, handling the calls they receive from genuinely concerned members of the public is a serious and delicate issue.
Scores of tales of ghosts and unexplained activity are known across Shropshire, while reports of UFO sightings are common across Powys.
Gareth Matthews, from Dyfed-Powys Police, said some reports were easily explained by non-supernatural means.
"A caller heard two bangs from the house next door and believed that it could have been a ghost," he said. "One caller thought that he may have been hearing voices and mentioned talking to ghosts."
While these may be explained away easily, Mr Matthews said the force had also received several more creepy reports as well.
"One individual stated that they saw a ghostly image and a picture of three faces of a family on the wall," he said. "We also had a caller who may have seen a ghost in the garden, and a caller talking about ghost riders in the sky 'going to get people'."
While there were no ghosts reported to police in Shropshire, West Midlands Ghost Club has paid several visits to the county in the last year on the trail of reported sightings.
Club members spent a night in Chetwynd, near Newport, in search of the ghost of Madam Pigott, and visited Lilleshall Abbey, one of the club's favourite haunts in Shropshire, where numerous ghostly monks had been reported.
Dyfed-Powys Police received a call from someone who was paranoid about being harassed by extra-terrestrials.
"He claimed that aliens embody themselves within humans which then enables them to operate amongst the human race without detection," Mr Matthews said. "We had two reports of aliens in the last year. The other was a caller who stated that they had aliens in their flat."
The county also saw two further out-of-this-world incidents.
"A caller stated that they and their partner had seen a UFO which was moving erratically but hadn't moved for the last 30 minutes," Mr Matthews said.
"Another caller reported a UFO stating that there were three objects in the sky, then that the lights were orange and that they could see four objects which were the size of a small house."
And not all the reports can be considered reliable.
In 1995 the fuzzy image of young girl was famously captured amid the flames as Wem Town Hall burned down. The photograph created international headlines and sparked the legend of The Wem Ghost, speculated to be 14-year-old Jane Churm, who accidentally started the disastrous great fire of Wem in 1677.
But Shropshire Star reader Brian Lear from Shrewsbury debunked the mystery in 2010 when he looked at a postcard of Wem franked in 1922 and saw a little girl standing in a doorway who looked exactly like the Wem Ghost, and concluded the spooky photograph had been faked.
Horrible histories haunting a host of landmarks
The Prince Rupert Hotel, Butcher Row, Shrewsbury
The Prince Rupert has had numerous sightings over the years. Ghostly figures have been seen to disappear through walls, pillows have been taken from rooms only to be found on the other side of the building, and a maid named Martha is rumoured to wander the staircase. Several guests have reported capturing some ghostly figures on camera.
l Ironbridge Power Station, Ironbridge
Several workers have reported seeing a ghostly black monk walking around the modern building and a phantom woman floating in the air. The power station was built partly on the site of a ruined abbey.
RAF Cosford Museum, Albrighton
The Avro Lincoln Bomber kept at the museum is said to be haunted by the ghost of Master Pilot Hiller, who loved the aircraft so much that he said on his last flight that he would "haunt his baby". Hiller was killed near Cosford in an air crash. Strange voices and other noises have been heard around the aircraft, and the ghost is also reported to be a handy mechanic, for whenever anything is needed, including old parts for the engine they always appear, often close to the person who needs it.
Ludlow Castle, Ludlow
The ghost of Marion La Bruyere is reputed to haunt the medieval castle, screaming on the anniversary of her death. Marion had been in love with an enemy of the castle's lord, but met him by lowering a rope for him to climb up. One night he left the rope dangling and the enemy forces were able to invade. Marion was furious with her lover and killed him with his own sword and then, realising what she had done, threw herself off the tower.
Whittington Castle, Whittington, near Oswestry
Mysterious balls of light and a horseman have been spotted at the castle, but it is ghostly children which are the castle's most famous apparitions. The youngsters are believed to have died in terrible circumstances after a cursed Elizabethan chest was opened.
Chetwynd Aston, near Newport
A ghostly figure believed to be Madam Pigott has been spotted many times on the A41. Having died in childbirth, Madam Pigott has been spotted carrying her baby and combing its hair.
l The old carpet factory, Bridgnorth
This factory was built on the site of a medieval friary. One ghost in particular, Old Mo, was seen by several employees. The ghostly monk, dressed in a white habit, was spotted climbing the cellar steps.
Haughmond Abbey, near Shrewsbury
Phantom monks have been see walking through the arched doorways of the ruin before fading away. One monk in particular has been seen several times.
l Churchyard of St John the Baptist, Ruyton-XI-Towns
Anyone brave enough to go into the churchyard at midnight may witness a thick mist rolling in. Soon after, a headless horseman rides in, vanishing into the mist and heading towards the old castle keep.
St Peter's churchyard, Easthope, near Much Wenlock
The sounds of an argument are often heard drifting across the churchyard. The participants are said to be two monks who now lie entombed next to each other. The monks were former residents of Easthope Manorhouse who one night began a fierce argument. They came to blows, fell down the cellar steps and were killed.