When adding a function in the prototype property of Object, ie :

#!js
if (!Object.noopFunc) {
	Object.prototype.noopFunc = function(e) {
		return "noOp";
	}
}

animations such as fadeOut raise an exception :

#!js
$("div").fadeOut(500, someCallback);

Uncaught TypeError: Object function (e) {
    return "noOp";
} has no method 'concat' 

Here is a sample traceback :

(anonymous function) jquery-1.8.2.js:8595
jQuery.extend.each jquery-1.8.2.js:605
createTweens jquery-1.8.2.js:8594
Animation jquery-1.8.2.js:8683
jQuery.fn.extend.animate.doAnimation jquery-1.8.2.js:9005
jQuery.extend.dequeue jquery-1.8.2.js:1894
jQuery.fn.extend.queue jquery-1.8.2.js:1937
jQuery.extend.each jquery-1.8.2.js:611
jQuery.fn.jQuery.each jquery-1.8.2.js:241
jQuery.fn.extend.queue jquery-1.8.2.js:1930
jQuery.fn.extend.animate jquery-1.8.2.js:9015
jQuery.each.jQuery.fn.(anonymous function) jquery-1.8.2.js:9100
myNiceEffectFunction jQueryBugOnObjectProrotype.html:17
jQuery.Callbacks.fire jquery-1.8.2.js:974
jQuery.Callbacks.self.fireWith jquery-1.8.2.js:1082
jQuery.extend.ready jquery-1.8.2.js:406
DOMContentLoaded