Now the couple say their children could have choked on the five pence piece as they got stuck into their dinner.
Mum Charlie Downs, 26, she was horrified when partner Leroy Dillon bit into the topping while enjoying his pizza at home near Plymouth on Saturday.
Leroy, 29, says he has been left with wobbly front teeth after biting into a slice containing a hidden coin, report the Plymouth Herald.
They have complained to Saltash-based Stop By and online take-out service Just Eat.
But takeaway bosses are refusing them a refund and accused the pair of "false allegations".
Just Eat said it was "disappointed" to hear about the incident and would be contacting Stop By to find out what had happened.
"How does a five pence coin fall into the pizza and then get baked in there?" asked Charlie.
"Our children were eating that pizza with us, they could have choked on it."
The worried couple say that they immediately got in touch with the restaurant to tell them what had happened.
Charlie said: "We asked to speak to the manager, but we heard nothing until someone showed up at our door with a new pizza.
"We showed them the pizza with the coin baked into it. They wanted to take it away with them but we said no.
"After that we contacted them again and they denied everything."
The takeaway deny the coin was baked into the pizza
The couple said that they then contacted Just Eat to report the incident.
Charlie said that her partner was left with two wobbly front teeth as a result of the incident, and that he will have to go to the dentist.
Harvey, aged eight, and six-year-old Kaitlyn were also enjoying the takeaway.
Charlie said: "It was one of the closest that didn't have a really long wait.
"Some places had a two hour wait but they were able to deliver in 45 minutes.
A spokesperson for Stop By in Saltash said it was not the first time the couple had complained.
He said they previously demanded a new pizza because theirs "was cold" - only to have eaten the cold one by the time their replacement, hot pizza arrived.
He added that the business was now considering what action it could take.
"After they called we sent a new pizza out of good will but they said that was not good enough. When the delivery driver arrived he asked to see the pizza and they refused.
"We also asked them to bring the pizza into the shop, which they refused.
The couple say the children could have choked on the coin
"We have been running for 27 years and we have never had a complaint like this before.
"We always try and keep our customers happy but not when they make false allegations.
"They will not be getting any compensation and because we have refused them they have gone to The Herald."
A Just Eat spokesman added: "We take food standards and hygiene ratings very seriously, as we work hard to ensure the best takeaway experience for our customers.
"As such, we actively engage with the FSA and our restaurant partners to help drive up standards across the industry.
"We were disappointed to hear about this particular incident and we will be contacting the restaurant to find out more.
"We have a dedicated customer service team in place, and have invested to make sure the right level of support is always there for our customers, whether by phone, email, or instant messenger."