Starbucks is issuing an apology after customers were sent into a frenzy over its new bear-shaped holiday cups.

Starbucks Workers United, representing approximately 9,000 baristas in 550 stores, has voted to strike on Thursday, Nov. 13 during the company’s ‘Red Cup Day’ promotion.

More than 12,000 baristas across 600 unionized Starbucks cafés have voted to authorize a national strike on November 13 — the same day Red Cup Day is set to take place. The potential walkout, organized by Starbucks Workers United, would mark one of the largest collective actions in the company’s recent history.

Starbucks union workes in 25 cities across the country plan to go on strike during one of the company's biggest days. Here's what to know.

"The excitement for our merchandise exceeded even our biggest expectations," Starbucks said in a statement to Fortune.