I can provide some information on the topic.
Putting cold pizza in a toaster is generally not recommended and can be potentially hazardous. Toasters are designed to toast and heat bread, not handle foods with toppings like pizza, which can have cheese, sauce, and other ingredients that may melt or drip during the toasting process. This can cause a mess inside the toaster and potentially lead to a fire hazard.
If you want to reheat leftover pizza, there are safer and more effective methods:
Oven: Preheat your regular oven to around 375°F (190°C) and place the pizza directly on the oven rack or a baking sheet. Reheat for about 5-10 minutes or until the pizza reaches your desired level of crispiness.
Microwave: While the microwave won't make the crust as crispy as the oven, it's a quick way to reheat pizza. Place a microwave-safe plate under the pizza and cover it with a microwave-safe lid or a damp paper towel to help retain some moisture.
Skillet or pan: Place the pizza in a skillet or pan on medium-low heat with a lid on top. This method can help make the crust crispy while also melting the cheese.
Remember to always be cautious when reheating leftover pizza or any food to avoid burning yourself. Always check the internal temperature of the pizza to ensure it's adequately heated before consuming.