When people decide to "free" their unwanted pets into the wild (Free Willy-style), little do they know the absolute chaos they're about to unleash on the environment and economy.
In short, setting your pets free could do more harm than good - so don't do it.
A handful of goldfish were released into a lake in Colorado. Now, much to the dismay of locals, there are thousands of them living there.
Goldfish are actually part of the Carp family and are native to Japan, so have no natural predators in America.
They have the potential to spread viruses and, if they escape lakes and head downstream, they could out-compete native fish (some of which are already threatened).
Removing these species also costs the government a lot of time and money.
In 1890, a fan of William Shakespeare wanted to bring the birds from Shakespeare's work to his home in New York.
So, he released one hundred starlings into Central Park and by 1928 those birds had bred so much that the population reached the Mississippi river.
By 1942 they had spread all the way to California, forming flocks of as many as one million hungry birds, driving off native species such as Bluebirds and Woodpeckers.
Today there are an estimated 200 million starlings in North America costing £800 million in damage to the agriculture industry.
Lizards: Pythons and the Argentine Tegu
In Florida, 84% of all introduced species stem from exotic pets which have been released into the wild.
Some of these include the Argentine Tegu, a lizard which can grow up to 4ft in length and lay 45 eggs a year.
Once established in an environment, they'll compete with local animals such as cats and dogs, and even native animals such as raccoons.
Watch the video for more unwanted pets who've caused havoc in their new-found environments.
Animals Who Need Hugs
(01 of19)
Open Image ModalIn this Feb. 9, 2012 photo, Meghan Caffery, a U.S. Customs and Border Protection Agriculture Specialist, hugs Izzy, an agricultural detector beagle whose nose is highly sensitive to food odors, at John F. Kennedy Airport's Terminal 4 in New York.(AP Photo/Craig Ruttle)
(02 of19)
Open Image ModalA woman hugs her dog during a memorial outside the Aurora Municipal Center July 22, 2012 in Aurora, Colorado.(Photo by Joshua Lott/Getty Images)
(03 of19)
Open Image Modal(04 of19)
Open Image Modal17-year-old evacuee Shoko Igarashi, hugs her dog who will have to be looked after by friends while she goes into a shelter in Koriyama in Fukushima prefecture, 60km west of Fukushima nuclear power plant on March 23, 2011.(Photo credit GO TAKAYAMA/AFP/Getty Images)
(05 of19)
Open Image Modal(06 of19)
Open Image ModalA woman cuddles her rabbit after an obstacle course of the first European rabbit hopping championships, which Lada Sipova-Krecova of Czech Republic won, on October 30, 2011 in Wollerau, Switzerland. (Photo by Harold Cunningham/Getty Images)
(07 of19)
Open Image Modal(08 of19)
Open Image Modal(09 of19)
Open Image Modal(10 of19)
Open Image ModalSpain's Queen Sofia hugs a 7-month-old panda cub during her visit to Madrid's Zoo on March 29, 2011 in Madrid. (Photo credit JAVIER SORIANO/AFP/Getty Images)
(11 of19)
Open Image Modal(12 of19)
Open Image ModalA 26-year-old chimpanzee named Pipo embraces veterinarian Eduardo Sacasa at the National Zoo, about 20 kms south of in Managua, on April 07, 2011.(Photo credit ELMER MARTINEZ/AFP/Getty Images)
(13 of19)
Open Image ModalMoose, a Leonberger, and Dr. Joe embrace during the second annual 'Meet the Breeds' showcase of cats and dogs at the Jacob K. Javits Convention Center on October 17, 2010 in New York City. (Photo by Michael Loccisano/Getty Images)
(14 of19)
Open Image ModalA nurse hugs Pisco, a 13-year-old therapy llama, during his visit to the Hospice of Saint John on September 1, 2009 in Lakewood, Colorado. The llama visits the hospice each month as part of an animal therapy program designed to increase happiness, decrease loneliness and calm terminally ill patients during the last stage of life.(Photo by John Moore/Getty Images)
(15 of19)
Open Image ModalEli the British Bulldog gets a cuddle from her owner Sue Leicity on Day one of Crufts, a four day dog competition, at the Birmingham NEC Arena on March 8, 2012 in Birmingham, England.(Photo by Dan Kitwood/Getty Images)
(16 of19)
Open Image ModalA woman hugs one of her monkeys at her house in Havana on October 20, 2010. (Photo credit STR/AFP/Getty Images)
(17 of19)
Open Image Modal(18 of19)
Open Image ModalA Romanian woman embraces her dog during an animal rights protest in the front of the Romanian Parliament building in Bucharest on April 11, 2011.(Photo credit DANIEL MIHAILESCU/AFP/Getty Images)
(19 of19)
Open Image Modal