Gloo Gloo, Sharky, Papsy and Bunny have become familiar names at day-care centres and schools around Germany. The adhesive animal characters, which come free with every purchase of €15.00 or more, have proven to be a playground hit.
But just as a market was developing, with parents trading online on behalf of their children, the supply ran out. The strength of public reaction was unprecedented.
Writing on the Facebook page of the discounter, one customer wrote "My eight-year-old is in tears. She's very disappointed in Lidl." Another said "By treating customers in this way you are alienating a loyal customer and destroying the illusions of my children."
Lidl is not the first German supermarket chain to use collectibles for children as a promotion strategy. Penny's Germany-themed "Unser Deutschland" picture range proved a hit with children, as did Real's Axterix marbles.
In response to a query from the website of Der Spiegel Lidl said it regretted that "despite generous planning, some branches no longer have sufficient stickers."
Targeting children is a lucrative marketing strategy for discounters. "Families with children are by the far the most desirable target group among supermarkets," trade expert Roland Bergel told the online edition of Der Spiegel.
"Companies cash in on children's desire to collect in order to lure their parents," Eckard Berner of the consumer advice centre in Baden-Württemberg told the website. "Here the relationship between parent and child is deliberately exploited to push up turnover."
It remains to be seen whether Lidl will reimburse customers who had purchased a special case in which to house their collectibles.