Creeper animation

1

I was wondering if anyone could help me out. I want to create an animation with a growing creeper. I’m not sure what would be a good approach - frame by frame, shape tween or maybe some coding.

I want to create something simillar to this:

http://www.templatehelp.com/aff/preview.php?aff=goodtemplatescom&skin=999&locale=en&currency=0&pr=yes&src=yes&nt=no&help=yes&sample=yes&faq=yes&nmg=yes&auth=yes&down=yes&chm=&hide_flash=0&search=&PHPSESSID=a370626d55cbcb7e14acba18a2917c30&referer=http%3A%2F%2Fwww.goodtemplates.com%2Ftemplates.html&i=14267