New Delhi, May 11 -- With just under a month until the FIFA World Cup kicks off, thousands of people are filling Argentine plazas strategizing to win a different game that has become a beloved part of the quadrennial competition: collecting and trading stickers to complete the official World Cup stickerbook.

For more than half a century, Panini stickerbooks have been a treasured part of the World Cup experience, with schools, plazas and even offices becoming zones to barter for coveted rare stickers and duplicates laid out ready to be discarded.

In South America, swapping stickers is even more important than simply collecting them, with WhatsApp groups, apps and websites popping up to facilitate the trades.

On Sunday, throngs of people...