meddle

Seems too complex to me :)

I think with this example you can create hierarchies easier.
jsfiddle

function ex (destination, source) {
  var p;

  for (p in source) {
    if (source.hasOwnProperty(p)) {
      destination[p] = source[p];
    }
  }
  return destination;
}

function extend (data, staticData) {
  var parent = this,
      child = function () {
        if (data.initialize) {
          data.initialize.apply(this, arguments);
        } else {
          parent.apply(this, arguments);
        }
      };

  ex(child, parent);

  if (staticData) {
    ex(child, staticData);
  }
  if (!data) {
    data = {};
  }

  child.prototype = ex(Object.create(parent.prototype), data);
  child.prototype.constructor = child;
  child.prototype.__super = parent.prototype;

  return child;
}

function Foo (a, b) {
  this.a = a;
  this.b = b;
}

Foo.prototype.c = function () {
  return this.a + this.b
};

var foo = new Foo(2, 5);
console.log(foo.c());

Foo.extend = extend;

Bar = Foo.extend({
  initialize: function (a, b, d) {
    this.__super.constructor(a, b);
    this.d = d;
  },    
  d: 8,
  e: function () {
    return this.a + this.b + this.d;
  }
});

var bar = new Bar(3, 1, 9);

console.log(bar.c(), bar.e());

var Baz = Bar.extend({
  initialize: function (a, b, d, f) {
    this.__super.constructor(a, b, d);
    this.f = f;
  },
  f: 2,
  g: function () {
    return this.a + this.b + this.d + this.f;
  }
});

var baz = new Baz(3, 1, 4, 6);

console.log(baz.c(), baz.e(), baz.g());