The value of [[Prototype]] of Array.prototype is the standard built-in Object prototype object (15.2.4).
The array prototype object is itself an Array. It has [[Class]] set to "Array" and length to +0, as well as the special [[DefineOwnProperty] method as per 15.4.5.1.
The methods defined on Array.prototype are all generic. You can use call and apply to supply different this values and if such value is not an array the function will still (try to) behave properly.
Arrays inherit valueOf from Object.