They made special cards, queued to wish him Happy Birthday, and one youngster brought a banana tied with a bow to help Ricky, the special-needs monkey, celebrate his 15th - and possibly last - birthday at Natureland.
Zoo curator Gail Sutton said the day was extra special as staff had thought Natureland was going to close on March 31, and would not have been open to celebrate Ricky's milestone.
"We didn't make any plans, and when we found we were definitely staying open longer we had three weeks to put together a birthday party for Ricky."
Mrs Sutton said the community had been supportive and donated time and energy to help the cash-strapped zoo mark the capuchin monkey's big day.
A cloud has hung over the future of Natureland and its inhabitants after the Nelson City Council announced a month ago that it planned to close the small zoo because it was no longer financially viable.
The council is now discussing proposals for the zoo's future, including one that is believed to have come from the Christchurch-based Orana Wildlife Trust.
Ricky, who was left badly brain-damaged after being brutalised by a jealous sibling when he was born, has been in the media spotlight following the council's announcement, with staff and the public expressing concern at what might happen to him should the zoo close.
Mrs Sutton said the turnout for Wednesday's party was great, and people had queued from 9.30am to get into the park.
She said the number of visitors was probably up on Ricky's previous birthday celebrations, possibly because it could be the last one he had at Natureland.
Ricky would be found another home if he couldn't stay at Natureland, she said.
On Wednesday, the birthday boy spent a lot of the morning wrapped in a rug to ensure he didn't catch a chill.
Among the young fans who gathered to give Ricky a gentle pat were Damien, 2, and Hayley Pettis, 11 months, of Motueka.
Their mother, Jody Pettis, said Damien had been excited to see Ricky, and had been chanting, "Monkey, monkey" as soon as he entered the park.
Tessa Moore, 4, from Wakefield also stood close by Ricky. Her mother, Sonia Moore, said Tessa was a huge fan of Ricky, and often went to Natureland with her grandmother.
Capuchin monkeys can live until age 40.
Natureland is now scheduled to close on July 4.