I have a Papa Johns story too!
This was years ago, but one time we got a BBQ chicken pizza. We were watching a movie in the dark, when one of my kids said his pizza tasted funny. I took it from him and went into the kitchen. Under the cheese was a blue substance, it reminded me of Comet cleanser. I lifted the cheese back further and found several spots of blue. I then took out the rest of the pizza and noticed a few more pieces had these spots.
I was freaking out, thinking my kids were eating some kind of chemcial. I called the pizza place and was told not to worry, they didn't use any type of blue cleanser. Nothing more, no apology, etc. I called the district store and spoke with another manager. He was at our door within 30 minutes, with new pizzas.
He looked over the blue spotted pizza and called the other manager to my house. That manager came and poked at the blue spots. Then he took a chunck of it and put it in his mouth.

Then he started to chuckle. He said, sorry, these are blue M and M candies. We have a bag of Star Wars ones and someone must have grabbed them and put them on the pizza by mistake!
This went all the way to the national office and we were given 30 free pizzas. Unfortunately none of us wanted pizza from that place anymore. I was giving out free pizzas for months.