JSFiddle - React, Tailwind, and code Playground

HTML

<div class="moreVideos">
<span class="mb">
    <a class="ml" href="#">
        <img src="http://i.ytimg.com/vi/qrO4YZeyl0I/default.jpg" id="thumb_qrO4YZeyl0I" class="mvThumb" title="Lady Gaga - Bad Romance">
    </a
</span>
<span class="mb">
    <a class="ml" href="#">
        <img title="Lady Gaga - Alejandro" class="mvThumb" id="thumb_niqrrmev4mA" src="http://i.ytimg.com/vi/niqrrmev4mA/default.jpg">
    </a>
</span>
<span class="mb">
    <a class="ml" href="#">
        <img src="http://i.ytimg.com/vi/qrO4YZeyl0I/default.jpg" id="thumb_qrO4YZeyl0I" class="mvThumb" title="Lady Gaga - Bad Romance">
    </a
</span>
<span class="mb">
    <a class="ml" href="#">
        <img title="Lady Gaga - Alejandro" class="mvThumb" id="thumb_niqrrmev4mA" src="http://i.ytimg.com/vi/niqrrmev4mA/default.jpg">
    </a>
</span>

JavaScript

$(document).ready(function(){

 $('a.ml').click(function(){
  loadAndPlayVideo( $(this).find('img').attr('id').replace(/thumb_/,'') );
  return false;
 })

 var timer,
  count = 0,
  cycle = function(el){
    var s = el.attr('src'),
     root = s.substring( 0, s.lastIndexOf('/') + 1 );
    count = (count+1)%4;
    el.attr('src', root + ((count==0) ? 'default' : count) + '.jpg');
 };

 $('.mb img').hover(function(){
   var $this = $(this);
   cycle($this);
   timer = setInterval(function(){ cycle($this); }, 1000);
 }, function(){
   clearInterval(timer);
 });
 
})