Are enums only named integers, types or neither of both?

Fun with enums in C#. Take one generic list that is created to store some Enum that you had defined previously and add few items in it. Iterate with foreach or GetEnumerator<T>() but specify some other enum then the original and see what happens. I was expecting InvalidCastException or something like that but it perfectly works :).

For the illustration let's take a simple console application and create two enums there: Cars and Animals:

    public enum Cars
    {
        Honda = 0,
        Toyota = 1,
        Chevrolet = 2
    }
    public enum Animals
    {
        Dog = 0,
        Cat = 1,
        Tiger = 2
    }

And do this in main method:

    public static void Main()
    {
        List<Cars> cars = new List<Cars>();
        List<Animals> animals = new List<Animals>();
        cars.Add(Cars.Chevrolet);
        cars.Add(Cars.Honda);
        cars.Add(Cars.Toyota);

        foreach (Animals isItACar in cars)
        {
            Console.WriteLine(isItACar.ToString());
        }
        Console.ReadLine();
    }

It will print this in console:

Tiger
Dog
Cat

Why is this happening? My first guess was that enum is not actually a Type by himself it's just and int but that's not true: If we write:

Console.WriteLine(Animals.Tiger.GetType().FullName); We will get his fully qualified name printed! So why this?