Razor in the apple

Answer 1

There have been people who inserted razor blades into apples and then gave the apples to trick-or-treating children on Halloween. The children would bite into the innocent-looking apple and severely cut their mouths. The razor in the apple became a catch-phrase for something dangerous being hidden in an otherwise benign object, like "a wolf in sheep's clothing." This phenomenon was one of the reasons that parents now insist that their children who go trick-or-treating eat only the treats that come factory-wrapped.

The phrase "Razor in the apple" means that there is something in the apple which makes your tongue feel like a razor. it could mean that the apple could not be a normal apple.