trackEvent patch example. Example of patching Google anayltics push function. As an example, overrides the _trackEvent method to pop an alert with the event details. Finally, call the real analytics function so as to not break the tracking.

trackevent_patch.js

<script type="text/javascript">
  (function(){
		var realPushFunction = window._gaq.push;
		window._gaq.push = function(params) {
			if (params[0] == "_trackEvent") {
				alert("category:  " + params[1] + 
					"\naction:    " + params[2] + 
					"\nopt_label: " + params[3] +
					"\nopt_value: " + params[4]);
			}

			return realPushFunction.call(window._gaq, params);
		}
	})();
</script>