Right click on the site(anywhere), click on inspect element, then select the console tab and enter the code below and press enter.
I'm using firefox, don't know if it works with other browsers.
Code:
javascript:(function(){function c(){var e=document.createElement("link");e.setAttribute("type","text/css");e.setAttribute("rel","stylesheet");e.setAttribute("href",f);e.setAttribute("class",l);document.body.appendChild(e)}function h(){var e=document.getElementsByClassName(l);for(var t=0;t<e.length;t++){document.body.removeChild(e[t])}}function p(){var e=document.createElement("div");e.setAttribute("class",a);document.body.appendChild(e);setTimeout(function(){document.body.removeChild(e)},100)}function d(e){return{height:e.offsetHeight,width:e.offsetWidth}}function v(i){var s=d(i);return s.height>e&&s.height<n&&s.width>t&&s.width<r}function m(e){var t=e;var n=0;while(!!t){n+=t.offsetTop;t=t.offsetParent}return n}function g(){var e=document.documentElement;if(!!window.innerWidth){return window.innerHeight}else if(e&&!isNaN(e.clientHeight)){return e.clientHeight}return 0}function y(){if(window.pageYOffset){return window.pageYOffset}return Math.max(document.documentElement.scrollTop,document.body.scrollTop)}function E(e){var t=m(e);return t>=w&&t<=b+w}function S(){var e=document.createElement("audio");e.setAttribute("class",l);e.src=i;e.loop=false;e.addEventListener("canplay",function(){setTimeout(function(){x(k)},500);setTimeout(function(){N();p();for(var e=0;e<O.length;e++){T(O[e])}},15500)},true);e.addEventListener("ended",function(){N();h()},true);e.innerHTML=" <p>If you are reading this, it is because your browser does not support the audio element. We recommend that you get a new browser.</p> <p>";document.body.appendChild(e);e.play()}function x(e){e.className+=" "+s+" "+o}function T(e){e.className+=" "+s+" "+u[Math.floor(Math.random()*u.length)]}function N(){var e=document.getElementsByClassName(s);var t=new RegExp("\\b"+s+"\\b");for(var n=0;n<e.length;){e[n].className=e[n].className.replace(t,"")}}var e=30;var t=30;var n=350;var r=350;var i="//s3.amazonaws.com/moovweb-marketing/playground/harlem-shake.mp3";var s="mw-harlem_shake_me";var o="im_first";var u=["im_drunk","im_baked","im_trippin","im_blown"];var a="mw-strobe_light";var f="//s3.amazonaws.com/moovweb-marketing/playground/harlem-shake-style.css";var l="mw_added_css";var b=g();var w=y();var C=document.getElementsByTagName("*");var k=null;for(var L=0;L<C.length;L++){var A=C[L];if(v(A)){if(E(A)){k=A;break}}}if(A===null){console.warn("Could not find a node of the right size. Please try a different page.");return}c();S();var O=[];for(var L=0;L<C.length;L++){var A=C[L];if(v(A)){O.push(A)}}})()
I'm using firefox, don't know if it works with other browsers.