Prototype in this Array slice call, why?

I was reading the MDN page for the JS Function's arguments variable:

https://developer.mozilla.org/en/JavaScript/Reference/Functions_and_function_scope/arguments

I understand that arguments is not an Array so this won't work:

var a = arguments.slice();

The solution on MDN is do do this:

var args = Array.prototype.slice.call(arguments);

Why use Array.prototype and not just Array.slice.call(arguments)? Is using the prototype significant here?