1. Prepare brownie mix according to package directions in a 13- x 9-inch pan. Prick tops of warm brownies at 1-inch intervals with a wooden pick, and brush with coffee liqueur, if desired. Crumble into small pieces.
2. Prepare pudding mix according to package directions, omitting chilling.
3. Place half of crumbled brownies in bottom of a 3-quart trifle bowl; top with half each of pudding, candy bars, and whipped topping. Repeat layers. Cover and chill at least 8 hours.
Note: For testing purposes only, we used Kahlúa for coffee liqueur.