So I have heard from a few different people that there are unaired Thundercats eps. Has anyone else heard this?
Chris here…
First I’ve ever heard of it, I must confess - where did you hear about it? 
The only unproduced episode I’ve ever heard of was an episode that Kimberly Morris wrote to be episode #130 called “Goodbye Jaga”, but which got pulled in favour of a more “open-ended” season finale, which became “The Book of Omens” - however, it was only an unproduced script, not an episode that was produced and then canned…
Take care…
heard it via word of mouth from 3 different people, none of whom know each other, which is what peaked my interest.
Have to back Chris up here - only thing I know about are unproduced scripts, specifically Morris’s. I don’t know of any episodes that made it past script stage that were never aired, however. Would be news to me.