Typically, when I have seen names that have similar things it is because the items are ripped from a disk and they have embedded into the title field.
When I have had the problem I removed the tags from the metadata of the file. Moved the folder out of plex, empty trash, clean bundles, and then readded the folder. So the only additional step would be to check the files for embedded information that could be getting read from the files themselves.
Jesus. I can’t believe that didn’t occur to me…I’m so used to properly setup MKVs at this point I didn’t even think about that. Thank y’all so much. facepalms himself to death :((
Handbrake is to blame. It embeds these lovely names into the ‘Title’ metatags of your mp4 files.
Do this:
Go to Settings - Server - Agents - Shows - TheTVDB
In there, grab the line ‘Local Media Assets’ with your mouse and drag it downwards, so it ends up being at the bottom of the stack of active agents.
Or fix the embedded ‘Title’ tag in your files, so they contain sensible data.
Try naming the top folder to ThunderCats (1985)
Afterwards, try Refreshing the show first.
If that doesn’t help, perform the Plex Dance with the whole show.
Is fixed. 
