Japan's plastic food samples are a multi-million-dollar industry, but one pastry shop's fake egg tarts are so life-like that its staff unwittingly sold five to customers.

Plastic food samples, known as "shokuhin sampuru," are made in painstaking detail to look as realistic as possible, from moisture droplets on a chilled glass of beer to the glistening surface of a bowl of ramen.

The plastic pastries at Osaka-based Andrew's Egg Tart are so convincing that even staff couldn't tell the difference and unwittingly sold five of them on Saturday to two unsuspecting customers at a pop-up stand near a station in Tottori in western Japan.

"We are very sorry that we mistakenly sold the samples," a company representative told AFP on Wednesday.

A clerk realized the mistake soon after the sale and the customers luckily returned the fake tarts to the stand before taking a potentially painful first bite.

Stickers will now be used to distinguish the real thing from the plastic desserts to avoid future custardy catastrophes.

That is if the store staff recognizes what's real and what's not.