I once found some glass in a John West can of fish I'd bought for the animals. I phoned the manufacturers helpline and was asked to return it for inspection. They tried to tell me the pieces are crystals from the sauce which could occur in the canning process and were not harmful. Well these "not harmful crystals" cut me when I picked a couple out, and they did go a bit over the top with compensation.
I've also found snails and stones in frozen vegetables, caterpillars in supermarket pre-washed ready to eat lettuce, and something absolutely unrecognisable in a tin of tomatoes. I always tip these out into a bowl first now to check and always wash any so-called pre-washed foods.
Buying all organic fruit and veg can be a bit of an education as well, but they do warn you that everything needs washing well before using and that you may find the odd lodger lurking in the green stuff.