The Simpsons in CSS with a little JS

simpsons.js

	(function () {
		var mouse = { x: 0, y: 0 };
		document.addEventListener('mousemove', function (event) {
			mouse.x = (event.clientX || event.pageX)/window.innerWidth;
			mouse.y = (event.clientY || event.pageY)/window.innerHeight;
		}, false);
		// shim layer with setTimeout fallback
		// @see http://www.paulirish.com/2011/requestanimationframe-for-smart-animating/
		var requestAnimFrame = (function(){
			return window.requestAnimationFrame       ||
				   window.webkitRequestAnimationFrame ||
				   window.mozRequestAnimationFrame    ||
				   function(callback){
				       window.setTimeout(callback, 1000 / 60);
				   };
		})();
		(function animloop(){
			requestAnimFrame(animloop);
			[].forEach.call(
				document.querySelectorAll('.eye,.left-eye,.right-eye'),
				function (eye) {
					var pupil = eye.querySelector('.pupil,.left-eye-pupil,.right-eye-pupil');
					pupil.style.position = 'relative';
					pupil.style.left = ((0.325+0.35*mouse.x)*100)+'%';
					pupil.style.top = ((0.325+0.35*mouse.y)*100)+'%';
				}
			);
		})();
	})();