I have been obsessed with 3D, ever since I was given my first View-Master in the 1970's. I've been an obsessive collector of all things stereoscopic ever since, and I've been taking my own 3D photos for the last 20 years or so.
I dread to think! I've been collecting them for decades and I'm still constantly finding new designs and new formats. I find it amazing just how many different devices have been produced - just to view a pair of images.
Yes indeed; there was an extensive library of cartridges available for this viewer - all with very high quality photos. I think you can still order them from the original manufacturer:
http://www.3dvision.ca/viewer_titles.html
Thanks! Ironically, he's actually a very timid cat in real life. I remember when he spent an entire day hiding under the bed in abject terror of the Christmas Tree....