The information could come from the creators at behind-the-scenes or keen observation of the series.
However one episode from second season was completely without the trivia-information.
Below is an example-scan of BCI's Volume 1 booklet that shows the trivia-information for episodes.
With Filmation He-Man though, James had collected quite a lot of trivia-pieces for each episodes. But in the actual DVDs themselves, only few were used. So there were some pieces of information that were left on the cutting-room floor (Same was with She-Ra DVD trivia, that was compiled by Alex Hawkey).
So when it came time to work on the MYP He-Man DVDs, James only wrote 2-4 lines for each episode, knowing that previously some had been dropped off.
With Volume 3 of the DVD-collection, there is a layout-error.
For episode 33 "Of Machines and Men" from the second season, there is no trivia-information. It appears that from all the printed booklets, the trivia-information for this one episode is completely missing.
Below is the trivia that is missing:* This episode showcases He-Man and Skeletor in their Battle Armor costumes, based on the toys of the same name
* This is Michael Halperin's only written episode of He-Man, surprising given his influence over the original and new series
So for all those who might have noticed this omitted piece of information, wonder no more!
A special thanks to James Eatock for sharing this information exclusively with us!
Be sure to check out James' self-published Cereal:Geek-magazine at this link as well as his The Unofficial Cartoon Guide to He-Man and the Masters of the Universe!