gistfile1.txt

var body = $(document.body);
var b = body.getElement("b");

//Listener class executes a logging function each time a method is called.
var Listener = new Class({
    listenStack: {},
    addListener: function(mth, fn) {
        this.listenStack[mth] = this[mth];
        this[mth] = function() {
            var rtrn = this.listenStack[mth].attempt(arguments);
            fn(rtrn, arguments);
        };
    }
});


Fx.Tween.implement(Listener);
Element.implement(Listener);

Element.addListener("tween", function(rtrn, args){
 console.log("returned: " + rtrn);
 console.log(args);
});

b.tween("padding", [0, 30]);
// I'd expect the console's to fire, but instead, TypeError: this.attachEvent is not a function