Here is a list of some common things that surprisingly contain animal derivatives and others that are safe. This is a product made when milk is heated with an acid, like lactic acid. Vegan-Rella is also totally vegan. Casein is also used in plastics, adhesives, and paint manufacturing. Wrigleys gum contains a vegetarian source of glycerine.
Many margarines contain whey.
May contain egg, especially if fresh. May be animal or fish derived. Animal fats used in most shop-baked pies etc. May be from animal bones too. An enzyme taken from the stomach of a newly killed calf.