Timaru woman Jo Wedlake's meal came with an extra message, which she found inappropriate.

A Timaru woman wasn't laughing after a bad-taste joke was handwritten on the inside of her takeaway pizza box.

Jo Wedlake and her family ordered a pizza online from the Timaru branch of Pizza Hut on Thursday night.

When the pizza was delivered, she opened the box and saw some writing on the lid but didn't take much notice of it.

She later read it and realised it was a "really inappropriate joke".

The joke read: "How do you get a fat chick into bed? A piece of cake."

At first, she thought maybe she should lighten up, or wondered if the message was directed at her. However, to her knowledge, she does not know anyone who works at Pizza Hut.

"It's not appropriate to be writing messages to random people."

She called the 0800 number to complain, but she said the phone operator was not really interested.

She also filled out the online feedback form.

"Whoever did it, I want an apology and to make sure it won't happen again."

Her worry was it could have gone to anyone, including young children. If her own 8-year-old son had seen it, she said she would have been "very angry".

It was also pointed out to her, it was unhygienic to have someone else's hands in the box.

A person from Pizza Hut did call to apologise on Friday, but did not offer an explanation as to what had happened.

That was not enough and Wedlake wanted to know that appropriate action would be taken.

As a matter of principle, Wedlake said she would not be going to Pizza Hut again.

Pizza Hut general manager of operations Jamie McKaughan said it was a one-off incident where a staff member had written a joke on a pizza box they thought was being delivered to a friend.

"We've spoken to the worker concerned and they are extremely embarrassed about the mix-up."

McKaughan said it was made clear this was "totally unacceptable" and further discipline was being considered.