The sale of a "once-in-a-lifetime" calf born with a smiley face on his coat means he will be bringing smiles to faces for the rest of his days — and help with the redevelopment of a Victorian hospital in the process.

Ripplebrook dairy farmers Megan and Barry Coster were amazed last week when they discovered a Holstein bull calf with "unbelievable" markings.

Since the ABC broadcast the story about the calf the Costers have been bombarded with requests from media from around the world, which quickly got old.

"We are pretty much over the circus — it's gone viral," Mr Coster said.

So the couple decided to find a buyer for Happy, which is where Farm World, a field day event run at Warragul's Lardner Park, stepped in.

Proceeds to fund hospital upgrade

Farm World chief executive Craig Debnam said a board member and livestock agent alerted him to the potential sale.

"So we sat down with the chairman and the deputy chair of our department said, 'Listen, this might be a great opportunity for Lardner Park to give Happy a really nice home it's literally around the corner from Barry and Megan's house,'" he said.

Farm World bought the calf for $10,000, which will be donated to the West Gippsland Hospital, which is being redeveloped after years of neglect.

Mr Coster wanted the money to go to the hospital because "all our children were born there and people we care about have been patients".

Mr Debnam says the special calf will be on display at Farm World, which started today and goes until Sunday, March 26.

"We're expecting 40,000 people through," Mr Debnam said.

Happy will live out his life on Warragul's rolling hills with other cattle for company.

"I think he's a once-in-a-lifetime calf which our patrons at Farm World will enjoy for many years to come," Mr Debnam said.

The Lardner Park site is a 120-hectare working farm that has a property manager to oversee the livestock.

Mr Debnam said the property conducted "Australia's only grass-fed steer trial," so Happy would have plenty of pals.

"We'll to look after this animal very, very well and he'll have a fantastic life," he said.

Happy calf 'not fazed by anything'

Hundreds of families, travellers and students turned up at Farm World on Friday to see Happy at his new home.

Excitement buzzed around the cattle pavilion station and many people posed for selfies with Happy.

For Bona Vista Primary School students, seeing Happy was the highlight of their Farm World excursion.

"Happy is up and about and walking around, and I can see his smiley face so clearly," Georgia said.

Another student, Jonah, said it was "pretty cool to see Happy because I saw him on social media last week".

"I spoke to my friends about him and this is my first time on a farm," he said.

Watching over Happy at Farm World is Karen Morham, a stud breeder who says there has been plenty of interest in the one-month-old.

"The feedback's been great and there's so many children and adults interested in seeing the smiley face on the side of Happy," she said.

"Happy is just happy — he's been snoozing and he is up, moving, and not fazed by anything."