Kids are mad over them, schools are banning them and adults are flogging them off online.
Supermarket chain Countdown's latest DreamWorks Heroes action cards are so highly sought after that despite being handed out free with every $20 spent in store, a full set is being sold on Trade Me for about $200.
The Press heard some schools have been forced to ban the new fad from schoolgrounds, and many Canterbury schools were either placing strict rules on trading, or using them as learning tools.
The promotion, which began on May 3, includes 42 collectable hologram cards featuring characters from children's movies The Croods, Kung Fu Panda, Puss in Boots, Shrek, Turbo and Madagascar. Stocks are expected to last until mid-June.
Principals' Federation president Phil Harding said the cards would be "like everything else, they too will pass".
"This sort of promotional material has been causing chaos for ages."
He suggested schools use them as learning opportunities, or ban them completely.
St Albans School principal Ginnie Warren said there had "certainly been an uptake" on the cards.
The school allowed trading in classrooms only, and if it "turns to custard" the cards would be banned.
Catherine Guyton, who is selling her cards online, had no idea why she began collecting.
"Our kids are grown up and I don't even know why I bought the book," she said.
She later saw how popular the collectibles were, and that the book alone was going for about $50 on Trade Me.
Adding the 115 cards she had collected, Guyton listed it starting at $30. It was up to $121 by the end of the week, with 967 views, 94 watchers and 38 bids. She was happy, "considering the outlay was $6 for the book, and you need to buy groceries anyway".
Christchurch Trade Me seller Mike Down collected a full book of the cards as a present for his nephew's first birthday but realising he would be too young to enjoy them, he decided to auction it to put the money in his nephew's savings account.
Not knowing its real worth, he "just thought I would put any old thing" and added a $500 "buy now". He got so many negative comments among its 1000 views, he removed the "buy now".
Another seller is up to $200 for 250 unopened cards.
Countdown Christchurch manager Tom Dear said trading was so popular, the company organised swap meets at all its stores.
IN AND OUT
Popular schoolyard crazes:
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