THE hottest toy this Christmas is selling for twice the retail price online on the Sunshine Coast as parents struggle to fulfill their children's wishlists.

Hatchimals, app-controlled eggs which hatch into animals, have disappeared from shop shelves almost as quickly as they appeared.

Kmart at Caloundra had about eight on the shelves on Tuesday which were gone by Wednesday as word spread on social media that some were available.

The Hatchimals were priced at $79.99 at Kmart but are for sale at $150-$179 online on the Sunshine Coast, and up to $400 interstate.

Toyworld Nambour owner Geoff Jensen said his store ran out out Hatchimals at least three weeks ago but was fielding enquiries every day for them.

"There seems to be one toy every year that everybody wants but can't get,” he said.

"They've sold out world wide and I think the only place you can get them now is on eBay.”

Mr Jensen said he knew of at least one customer who had bought one online, and although he was unsure of the price, thought she paid $200 or more for it.

He was not sure why the Hatchimal had proven such a hit this year but said its popularity was at least partly due to "the look of it, and the feel of it, and the more you interact with it, the better it gets with you.”

He said most but not all of the Hatchimals had been sold as children's presents "but some of them have gone to retirement homes where they can't have pets”.

Kristi Dorward, of Wurtulla, scoured toy shops and variety stores between Gympie and North Brisbane for Hatchimals after three of her five children each asked for one for Christmas.

"People were selling them for $300 online and I can't understand why anyone would pay that much,” she said.

Mrs Dorward eventually got a call from Big W at Coolum to say they had one available, and was lucky enough to pick up two more while shopping at Kmart Caloundra this week.

She said the Hatchimals' popularity seemed to have caught retailers by surprise.

"They said we didn't realise they were going to be so popular so we only ordered a small amount in,” she said.

Mr Jensens said enquiries for Hatchimals were starting to slow down as parents gave up the hunt.

"I think most people are starting to realise they can't get them,” he said.

He said Snuggles the Puppy, a life-like toy dog which responded to pats and tickles and had six different play modes, was firming in the popularity stakes as parents sought an alternative to Hatchimals.

Also popular this Christmas were Shopkins, action heroes such as Spiderman and Teenage Mutant Ninja Turtles, Star Wars toys, and regular favourites such as slot car racing sets and Lego.