MyObject = Class.create();
MyObject.prototype = {
  initialize: function(key) {
    this.FooKey = {What: key };
  }
};

AnotherObject = Class.create();
AnotherObject.prototype = {
  initialize: function(key) {
    this.BarKey = {Who: key };
  }
};

/* --- */
var singletons = {
  MyObject: {prop: 'FooKey', key: 'What'}
  ,AnotherObject: {prop: 'BarKey', key: 'Who'}
};

// shared bound constructor
function singletonInit(type, data) {
  this[type.prop] = {};
  this[type.prop][type.key] = data;
}

for (var name in singletons) {
  window[name] = Class.create();
  window[name].prototype.initialize = singletonInit.bind(singletons[name]);
}