I hereby announce that my hand-written script, the YouTube Link Popups, is now on public beta.... and for the third time at that! :P
Now, you should be able to see a popup when you hover your pointer over a link to a YouTube video in the articles. That popup will show, among others, the video's thumbnail as well as a few vital information such as upload date, duration, views and ratings.
Here's a screenshot of the popup in action (the yt link itself is the one underlined):
As a heads-up: I pulled back the beta the last two times because I think the popup is messing up the Visual Editor. That's purely speculation though, as at that time the Visual Editor itself is fairly new, and new stuff are bound to come with problems. Still, if you find that the VE persistently go FUBAR around you from here onwards, and you suspect this script might have anything to do with it, please inform me by posting in this thread. Otherwise, you'll do wise to contact staff directly.
Other than that, if you have suggestions, feedbacks, comments, and problems regarding the popup, feel free to add a reply to this thread.
Have fun! :D