I'll just go with stuff from the 90s anime since manga production trivia is easier to come across.
- The shade of red on Sailor Moon's ribbons/gloves/boots/choker (and by extension the front ribbon on the juban middle school uniform) are a pink-ish or magenta tint of red, not pure red. It can be hard to tell since the footage quality in the 90s anime is all over the place, even after it was remastered. Looking at decent scans of the original cels (or Marco Albiero's images, since they use the exact same colors as them) show this alongside remastered manga illustrations.
- Kotono Mitsuishi had surgery and was hospitalized during the recording sessions for episodes 44-50 because because she actually had an ovarian cyst. Not appendicitis as is often claimed.
- Keiko Han, who voiced both Luna and Queen Beryl, asked the staff if she could have a break in-between her takes during the finale. This was because one scene would have Luna sobbing and the next would have Beryl laughing manically, so she needed to mentally prepare herself more for those totally opposite roles.
- The iconic Moon Prism Power Make Up transformation sequence was animated by the director of Trigun. If one assumes that the laserdisc extra showing the animation process used footage of the staff as they actually made it (rather than a re-enactment,) that would mean Kunihiko Ikuhara storyboarded the sequence as well. He also storyboarded Venus' transformation.
- Ikuko Itoh began to get the idea for Princess Tutu while she was working on Sailor Moon and Maho Tsukai Tai
- Hideaki Anno, the creator/director of Evangelion animated several parts of episode 103 (Sailor Chibimoon's introduction episode, directed by Kunihiko Ikuhara) and did the storyboards for Uranus and Neptune's transformation sequences. Rei Ayanami from Evangelion was also named after Rei Hino, Ikuhara's favorite character, as an attempt to get him on board with working on the show with him.
- More about Ikuhara. Anno claimed at an event that once he became the series director, there were periods of time where he would work for four whole days without any sleep.
- As someone previously noted, one of Kotono Mitsuishi's absolute favorite moments in the 90s anime was in episode 125, where Usagi is screaming "Crisis, Make Up!" to try and become Super Sailor Moon in order to enter Pharaoh 90 and save Hotaru. One of the biggest reasons for this was that the animation was going to be done *after* the recording sessions, not before. This meant that she didn't have to worry about syncing up to mouth flaps and could perform as naturally as she wanted. The animation team and the director loved her take and used it for the episode.
-Speaking of Kotono Mitsuishi's performances as Sailor Moon, one of the audio drama cassette tapes has several moments from episode 45 and 46 which included most of Usagi's memorable lines from the former re-recorded. The staff watching her in the recording booth were really impressed with her as she became so swept up in the role, she was actually sobbing and her nose was running (which is probably something that happened before with recording sessions in SM, but still. If you ever hear it, it's a chilling and heart-wrenching performance.) She said she was thinking about what both Usagi and the other girls were going through during those events. Also in the Classic season memorial, she voiced over Usagi's dying inner monologue where she reminisces her days as a normal girl and wishes to go back to them. It also sounds very heartfelt. Maybe this was sort of her making up for her absence during that time? The drama mentioned before is called "Prelude to Romance," and it's a crime nobody has ever translated it.
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