CATS. Oh yeah, there are (at least) 3 things wrong with this that make the console.log on line 9 not work.

gistfile1.js

var Kitten = function(name) {
	this.name = name;
	var mouseCount;
	
	this.init = function() {
		this.stalk(function(count) {
			mouseCount = count;
		});
		console.log('You found a kitten! Congrats! Its name is ' + this.name + ' and it caught ' + mouseCount + ' mice');
	};
	
	this.hunt = function(callback) {
		// some ajax thing
		// executes 'callback' when it's finished
		// (we'll fake it - you can assume it's successful)
		window.setTimeout(function() {
			// will always return a value between 1 and 3
			callback(Math.floor(Math.random() * 3) + 1);
		}, 1000);
	}

	this.walkAcrossKeyboard = function() {
		return 'xcxcxcxcccccccccccjjjjjjjjjjjjjjjjjjjjjjjjj';
	};

	this.init();
}

var myKitten = new Kitten('Charmander');