If you are using backbone (and backbone.marionette) in a browserify managed project, you will likely run into issues with underscore (at least if you manage your dependencies with npm). Each package, that has underscore as a dependency, will require its own version of underscore (making your bundle file contain multiple versions of underscore). Back in the days, you could shim backbone and underscore like:
browserify({
	shim: {
		'underscore': {
			path: './node_modules/underscore/underscore.js',
			exports: '_'
 },