Pizza Hut has pie on its face after an employee at one of its Singapore restaurants wrote "Pink Fat Lady" on a customer's receipt.

Aili Si said she noticed something strange on her receipt after she ordered a pizza at the chain’s location in Bukit Merah, about 3 hours from Kuala Lumpur, the Straits Times reports.

Si posted a picture of the receipt with “Pink Fat Lady” scrawled on the bottom on Pizza Hut Singapore's Facebook page Sunday night, saying, “I don't think it is nice for your staff to describe me as such on my receipt,” she wrote. "Just feel insulted. What's wrong being plus size? I'm a customer and I pay for my pizza! Not that I'm get it for free!"

Many took to social media urging Si to demand an apology from Pizza Hut. Some even suggested she ask for free food.

On Monday, Pizza Hut responded to Si's post, writing that the incident "definitely rocked us in our seats."

Later, Pizza Hut Singapore's senior marketing director Juliana Lim said that they reached out to Si and apologized for the incident.

"She expressed her understanding of the matter, which was a genuine error of judgement with no intent to offend, and has accepted our apology," said Ms Lim.

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Si thanked the pizza chain for addressing her concerns, but urged others to “be sympathetic” and think about what "an obese individual may be facing."