Youtube Panel

How would I code a panel that shows a youtube video? I remember there was one that played look at my horse in gmod 12.

You can use DHTML panel and this:

<iframe width="420" height="315" src="YOUTUBE_URL_HERE" frameborder="0" allowfullscreen></iframe>

So basically I can make a panel model and use DHTML to show the visual?

Use that format for the link, and just load that link onto a dhtml panel.