How to bring up the iTunes podcast video window?
After an hour or so of fiddling and I realize that the TED podcast has the word "with video" attached to it and so I tried searching the store for the video version and boom! There it is, the version of the same podcast I've been listening to but with video. Playing episode in that podcast pops open the video window just fine.

So in case anyone else stumbling onto this:
Make sure you are subscribing to the version of the podcast with video.

You can tell quickly by looking for the little monitor icon next to the episode title:



Sorry for the trouble guys.