When toy company Build-a-Bear’s “Pay Your Age” promotion was announced on Monday, parents and kids celebrated: On Thursday, July 12, families could walk in and pick out a plush toy merely for the cost of their child’s age.

But by 11:30 a.m. Eastern time in the U.S., the long lines caused the company to put out a notice on social media that the deal had changed; the number of people who could take advantage of the promotion would be limited due to safety concerns.

Fights broke out between parents who were waiting in line in the U.K., as Unilad reported, with some having to stand in line for up to nine hours before they made it through the store doors.

Angry parents took to social media in both the U.S. and the U.K. to vent their anger and angst, using the hashtag #Buildanightmare; some parents reported waiting up to six hours in the U.S. to buy a plush toy.

Build-a-Bear representatives called the promotion “overwhelming and unprecedented” in a statement to USA Today’s All the Moms.

The company said it was “working to address the situation,” saying it would “reach out directly to our valued guests as soon as possible.”

It was a smart idea on the marketing side. To participate in the “Pay Your Age” promotion, adults had to enroll in the free Build-a-Bear Bonus Club rewards program — and provide an email address.

Related: As Toys ‘R’ Us Closes, Adults Are Having All Kinds of Feelings

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Build-a-Bear is expected to contact its customers via email.

Deirdre Reilly is a senior editor with LifeZette. Follow her on Twitter.