Those two are EXACTLY the ones I had in mind! 
We only see the footprints of the Wallies and Lion-O mentions the Miggit Swarm Monster when he and Mandora are flying towards the Living Ooze. I think there is a small illustration of this creature on the map of Third Earth that was printed in one of the TCats comics.
You are the winner of this round, Zax! :thumbsup I think the only time youâve ever struggled answering a trivia question was when the question was wrong! LOL! :biggrin
There is, yes! I wonder what the intention wasâmaybe something like Mumm-Raâs locust swarm that became a giant locust? âMiggitâ is close to âmidgeââŚ
Ha! I donât know if thatâs true. I feel like Iâve been stumped once or twice! [emoji28]
Anyway, new question! Many episodes start with Mumm-Ra bemoaning the many times the ThunderCats have foiled him, as the cauldron displays clips from past defeats. But in âExcaliburâ, one of these flashbacks has something wrong with it. Whatâs the goof?
Any takers on this one? I can offer up a screenshot as a hint, if thatâs helpful.
Thatâs a tough one. Iâve just watched the sequence and canât think. Did they forget to keep the cauldron bubbles overlaid to remind us where the flashbacks are being viewed?
Also that episode includes a flashback of Lion-O using the catchphrase because they couldnât crowbar it into the main happenings, which for me is just the most insane thing. It annoys me that they had the catchphrase save the day so much especially in the later episodes, but the use of it in a flashback here just so they could get it in was just stupid.
No, thatâs not what I had in mind. Itâs a visual difference between one of the flashbacks and the scene as it played in the source episode. But itâs also an inconsistency within the flashback itself, which is how I noticed it.
Like a mirror image?
Is it the flashback from The Astral Plane, in the original Lion-O appears as a giant but he seems smaller in the flashback?
Nope, but good guess!
No, itâs more straightforward than this. Think about simple mistakes that could be made when reanimating a scene.
Is it the Cat Symbol in the same episode? Did it originally shoot out of the symbol on the front of Cats Lair? Because it doesnât in the flashback!
I watched that scene a couple of times and I too am stumped. Canât seem to spot the error. 
How about another hint? Itâs in the âReturn to Thunderaâ flashback.
Is it that in the clip from the Astral Prison the beam from the sword appears long before he shouts âHO!â
OK, Iâve just looked at both âExcaliburâ and âReturn To Thunderaâ and I think I might have it, but could just as easily have been my eyes playing tricks on me.
In âReturn To Thunderaâ, the Mutant Warbot simply blows itself out of existence, but in the flashback shown in âExcaliburâ there is an explosion but the machine is then simply seen falling over.
At least thatâs what I think I saw.
Note to self, read all the comments properly before trying to answer. :laugh
:roflmao:roflmao:roflmao
No, the explosions are identical. The inconsistency is earlier in the sequence.
Ha! I figured youâd read it eventually. [emoji6]
Is it the background on which Lion-O is standing as he has his sword raised? In âReturn to Thunderaâ itâs concrete slabs but in the flashback in âExcaliburâ its grass.
Ding ding ding! âReturn to Thunderaâ on the left, âExcaliburâ on the right.
https://uploads.tapatalk-cdn.com/20210729/f4fd29fc3d65a65e2343dd4527a37957.jpg
I didnât mean for this to be so challenging! But once I spotted it, I was excited to share it here. [emoji846] Youâre up, Wilycub.
ETA: Credit to Booshman for the remastered episodes, now my preferred source for screenshots!
Thanks, Zax! I do find this error quite intriguing. It shows that the animators re-shot the entire sequence rather than just edit in the already shot footage from the earlier episode. I canât think of any reason why they would do it this way especially since it is very time consuming (and prone to errors, as you showed in your question) 
Maybe they didnât have any copies of the original footage after having sent it to the US?
I canât think of any decent trivia question that hasnât been asked already. So Iâll just post a screenshot and see who can identify the episode it is from. Here it is:
Is it from âMongorâ?