The classic Contra cheat code in jQuery

jquery.konamiCode.js

(function($){
	
	$.fn.konamiCode = function( callback ){
		var current_keys = [],
			current_keys_str = '',
			unlock_code = '38 38 40 40 37 39 37 39 66 65';

		$('body').on('keydown',function(e){

			current_keys.push( e.keyCode );

			current_keys_str = current_keys.join(' ');

			if ( unlock_code.indexOf( current_keys_str ) !== 0 )
			{
				current_keys = [];
			}

			if ( current_keys_str === unlock_code )
			{
				callback();
			}
		});
		
		// maintain the chain
		return this;
	};
	
})(jQuery);