Mad apple is a common term used for different types of fruits, such as apples, tomatoes, and eggplants. These fruits are also known as nightshades. They belong to the same plant family, Solanaceae. The term "mad apple" is used to describe these fruits because they were once thought to cause madness and hallucinations when consumed. However, there are several other terms that are used to refer to these fruits. For example, tomatoes are also known as "love apples." Eggplants are sometimes referred to as "aubergines." Apples, on the other hand, are often called "pippins." Regardless of what they are called, these fruits are all delicious and worth adding to any meal.