Using DayPilot Pro 7.7.787 and later (see the sandbox at http://javascript.daypilot.org/sandbox/) you can do this:
dp.onEventClicked = function(args) {
new DayPilot.Bubble().showHtml("Event details: " + args.e.text(), args.div);
};
Previous versions don't store the event div in args (args.div). This div is used to calculate the bubble location (it will be desplayed above the event).