Video Thumbnail Help!

I know this feature exists and I have been trying to locate it for days now. If anyone could please help. I am looking for a plugin that allows featured images on the homepage to open to videos. Almost like a shadowbox effect. I have installed shadowbox and it works on images within actual posts so when i click on them a smaller window opens within the page and plays a video. I would like this also for the featured image thumbnails on the homepage. someone please help!! thank you!