It's easy to see how anyone can fall for their cute tiny trotters.
Paris Hilton has one, and Katie Price was even given one for a wedding present.
'Micro-pigs' are sometimes described as the tea-cup sized pet which can be perfectly house-trained.
The animals are becoming more popular in the UK but the RSPCA says it's worried about their welfare and about owners who are sometimes misled about looking after them.
Lisa Turk, from Telford, bought a micro-pig after seeing an advert in a national newspaper.
She says when she bought Digby he was small enough to hold in her hands, and he lived in the lounge.
The breeder told her that the pig would eventually grow to around 40cm (16in) high.
However just 10 months on, he is 55cm (22in tall) and weighs 44kg (98lbs).
Digby has another year of growing left and Lisa says she's surprised at his size: "He's already got a 34in (85cm) waist, which is bigger than my boyfriend's."
She tried moving the animal into her garden but it soon turned into a muddy mess. Now she pays £60 a month for him to live on farmland.
'Destructive and aggressive'
The RSPCA says Lisa's case is not a one off.
Rachel Rocksborough, from the charity, told Newsbeat that people should think carefully before buying one.
"So called micro-pigs are created through selective breeding so the smallest pigs mate.
"It often involves in-breeding which can result in a higher risk of deformities.
"We are really concerned and believe no animal should be bred purely based on how it looks."
As well as the problem of micro-pigs growing too large, the charity also warns that no pig should be kept indoors - or alone.
"Pigs are meant to be kept outside, and in groups," says Rachel.
"If they are not, they can end up getting destructive and aggressive towards people."
Lisa has now bought two piglets to keep Digby company (she says they live in the 'Pig Brother House'), but she's also urging people to look beyond the pigs' cute appearance.
"I am worried people will go out and buy a micro-pig for Christmas and not realise what can happen.
"Digby is so loved though, I would never dream of getting rid of him. He's on Facebook now and has over 200 friends."