Flushed into the sewers, only to develop super powers as a result of mutations – we all know the story of how the Teenage Mutant Ninja Turtles came to be.
And it seems as though something similar is responsible for the mysterious appearance of two turtle-like creatures the size of dinner plates sighted in the centre of Strabane in Co Tyrone.
The two reptiles, now identified as red-eared terrapins, were spotted basking on a log in the Mourne River by a sharp-eyed 12-year-old who was walking her dog.
Cora Madden said: "I had taken my dog out for a walk on Thursday and I had heard there had been sightings of otters in the Mourne River, so I decided to stop and have a look.
"I glanced at the log and then I looked again because it was moving. Then I realised it was a turtle, so I phoned my dad and asked him to come over with the camera.
"Everyone has been trying to look for them since that, but nobody would even believe us at the start, so it's good that we got the photos before they swam away."
Her dad Paul says he thinks they are red-eared terrapins, which are supposed to be quite aggressive, and he believes they may have been flushed into the sewers by their owner.
"They're not native. It's off the main street in Strabane – the river goes down the back of it and it's been low for the past couple of days, so there was a sandy bank which was the right place for them," he said. "There's a 30ft wall down to the river and there's no way you can get down to it, so they would be safe enough.
"Lots of people have been down looking for the turtles and everyone is talking about it round the town."
The terrapins are definitely not native, according to Dr Jade Berman of Ulster Wildlife.
"This happens in places where they've grown too big for the tank, or someone doesn't want them any more, and they have popped them in the river and the animals have survived," she said.
"In some areas where this happens, they are seen as a bit of an invasive species as they can pose a threat to local turtles, although we don't have any freshwater turtles here.
"The young are carnivorous, eating insects or whatever they can catch, and as they grow older they become more herbivorous.
"They aren't dangerous to people, but I wouldn't stick my finger in their mouth!"
And she cautioned against dumping unwanted pets in the wild as this can be the way invasive species gain a foothold in new habitats.
"There were two turtles here and that is enough to breed," she said.
"If you dump them in the river, they might not survive.
"But also, they might survive and have an impact on native wildlife in the river," Dr Berman said.
The red-eared terrapin is a semi aquatic turtle which is the most popular pet turtle in America. It is easy to maintain as a pet. The animal is native to the southern United States and northern Mexico, but has become established in other places because of pet releases. It has become an invasive species in many areas, where it outcompetes native species.
... and six other visitors who turned up where they were least expected
1. Sewage workers in Ballyclare found a kitten battling to get out of a treatment works. An NIW employee heard a noise and when he investigated he saw a little kitten struggling in the inlet chamber. His efforts to rescue the kitten weren’t appreciated and when he tried to dry it off, it became frightened and tried to scratch him.
2. In 2007, a seal halted landings at City of Derry Airport on New Year’s Eve as it flopped on to the runway. Firefighters managed to remove the seal, and place it back in the water as the airport is located beside Lough Foyle. But staff were astonished as it reappeared the next day. It was taken to a seal sanctuary in Portaferry where it is called Frankie.
3. Twitchers called it the equivalent of seeing “Elvis walking through Belfast city centre”. A bird called the Pacific Loon appeared thousands of miles from its usual home. It's rarely seen away from its native lands along the Pacific coast of North America but it turned up on the waters of Lough Fea near Cookstown.
4. In 2013, six macaques escaped from Belfast Zoo and were spotted in a whole host of strange places. One was spotted up a tree in Gideon’s Green while another was captured by zookeepers running around the grounds of Belfast Castle.
5. Earlier this year a search was on for a wallaby and baby joey which escaped in Co Down. The marsupials are native to Australia but were reported as having escaped in the Knocksticken Road area of Clough, Downpatrick. However, both animals were discovered dead close to the area where they had gone missing.
6. Scores of onlookers flocked to the Red Bay pier near Waterfoot last September when a rare deep sea whale was washed ashore and died. At almost nine metres long, the baby Sei whale was spotted beside Red Bay pier by fishermen. It is believed the whale may have lost its mother or become ill. Severe weather — which had hit the north coast at the time — can sometimes cause the beaching of whales. Ballycastle Coastguard tried to refloat the whale but failed.