McDonald’s is seeing its largest driver of Happy Meals since it included mini Beanie Babies with kiddie meals way back in the 90s. But with demand so high, the “happy” part of the partnership is souring.

This week, McDonald’s launched Pokémon Happy Meals to mark the 25th anniversary of the franchise. Each meal comes in a Pikachu box along with a pack of four Pokémon trading cards (including a McDonald’s-exclusive holographic card) and a surprise gift. There are more than 50 cards to collect. The strategy is paired with new Pokémon stickers in the McDonald’s Happy Meal app and Pokémon-themed coloring and activity pages kids can download at happymeal.com.

In a sign of a great brand partnership strategy, McDonald’s Pokémon Happy Meals are reportedly going out of stock at some locations and people are sharing their efforts to buy as many Happy Meals as they can, just to get their hands on the cards. Meanwhile, scalpers are selling boxes containing more than 100 packs of the new cards on eBay for up to $1,000, with individually sealed packs selling between $5 to $20.

Customers are turning to social media to complain about scalpers and the fact that, with so many people buying up the boxes in bulk, little is left over for the kids who aren’t looking to make money, but just want to collect the actual cards.

Some people are even ditching the food entirely or donating it to charity just to get to the cards.

It’s unknown if some McDonald’s are limiting the amount of Happy Meals each customer can buy at this time. McDonald’s did not return a request for comment. The new cards come after a successful Pokémon Happy Meal run in Japan in 2002.

The brand has been silent on its social channels about the new Happy Meals but did announce today that a customer favorite—Hi-C Orange Lavaburst—will be coming back to U.S. menus by summer 2021. McDoanld’s did create a video promoting the partnership on its Happy Meal website.