With summer on the horizon and the easing of lockdown restrictions, the UK has seen unprecedented demand for Flake 99 ice creams.
Supply has struggled to keep up and the beloved 99s are now at risk of vanishing from shops, vans and ice-cream parlours, the Irish Mirror reports.
The ice cream toppers are half the size of the Flakes sold at newsagents and petrol station counters.
"We are seeing a recent increase in demand for our Cadbury 99 Flake in the UK and Ireland that we had not expected," Cadbury owner Mondelez said after confirming the shortage.
The news has caused alarm on Twitter with some proposing contingency plans.
Many have suggested alternative chocolate toppings that could be used to substitute the 99 Flake during the shortage.
Only the UK and Ireland are thought to have been affected.
Mondelez did not say how long it expected the shortage to last.
However in a statement, the company said: "The product is still available to order and we're continuing to work closely with our customers."
The majority of the 99 Flakes sold in the UK are made in a factory in Egypt, with some also arriving from a facility in Coolock in Ireland.
The term 99 Flake is often thought to indicate the price of the ice cream it accompanies but Cadbury says: "The real reason for '99' Flake being so called has been lost in the mists of time."
But it points to one explanation suggesting the name takes its inspiration from the former Italian monarchy after a Cadbury sales manager witnessed ice cream makers - who were originally from Italy, but working in County Durham - cutting flakes in half and adding them to cones.
"In the days of the monarchy in Italy, the King has a specially chosen guard consisting of 99 men, and subsequently anything really special or first-class was known as '99' - and that is how '99' Flake came by its name," Cadbury said.
Another claim states that it originated from Portobello, Scotland, where Stefano Arcari who had opened a shop in 1922 at 99 Portobello High Street.
Arcari would break a large "Flake" in half and stick it in ice cream but the name came from the shop's address.
Elsewhere, another address-based claim for the beloved ice cream is made by the Dunkerleys in Gorton, Manchester, who operated a sweet shop at 99 Wellington Street.
The report states that: "The 99 is so-called in honour of the elite guard made up of 99 soldiers who traditionally protected Italian monarchs.
"The chocolate maker borrowed the number name to appeal to expat Italians who dominated the ice-cream business in Ireland and Britain at the time."
