Sailor Moon seems to have originated the Toast of Tardiness trope.

That I seem to be the first person to propose this theory is interesting.  Because AniTubers putting together montages of famous examples of this trope in videos mostly about something else seem to know they can’t find an older example, if there is one it must be some super obscure old High School Anime forgotten by everyone but someone working on the 90s Sailor Moon Anime, and thus Sailor Moon was still clearly what popularized it.

The origins of this Trope is worth investigating since it’s actually NOT accurate to real world Japan.  In Japan, even casually walking while eating is considered Taboo because it’s disrespectful to the Labor put into producing it.  I learned about this interesting fact from reading the article linked below this paragraph.  Some things are common in Anime precisely because their Taboo in real life, but this is an oddly specific thing to be rebellious about, so there must be more to it.

https://honeysanime.com/editorial-tuesday-anime-and-real-life-running-with-a-slice-of-toast-in-their-mouth/

Project A-Ko does feature the lead running to school late, and shows her eating some food earlier, but not at the same time.  So maybe it played a role in inspiring this visual, but it’s not fully formed.

Here’s the thing I find interesting.  Every example of this cliché since the Spring of 1993 has either been in a pilot episode, or a parody of what a Generic High School Anime pilot looks like (such as it’s use in the finale of Neon Genesis Evangelion), or both at the same time like Attack on Titan Jr High.  But for Sailor Moon it’s not originally a pilot trope, it’s in no version of Usagi’s origin story, not the Manga or the 92 Anime Pilot or Crystal’s.

In Sailor Moon we first see this happen in episode 39 Let’s Become a Princess: Usagi’s Bizarre Training, which in the DiC Dub was episode 37 and titled Little Miss Manners, written by Shigeru Yanagawa and directed by Hiromichi Matano.  This gag actually bookends the episode appearing at both the beginning and end.  

However a few months later the first episode of Sailor Moon R, the beginning of the Doom Tree Saga, and episode 47 of the show total (41 of the DiC order), is very much a reboot, it’s like a new pilot repeating many beats of the original pilot.  But now the running late with Toast in Mouth is added, being a visual that must have stuck with someone after seeing it in the Princess episode.  

This episode was named Moon Returns: The Mysterious Aliens Appear and by DiC The Return of Sailor Moon.  It was written by Shigeru Yanagawa and directed by Kazuhisa Takenouchi (it would be this exact same combo who would end the Doom Tree Saga).  So the common denominator here is Shigeru Yanagawa.

Given that homevideo was only starting to take off in the early 90s, it wouldn’t surprise me if for a while after that episode aired in 93 many people misremembered this visual as having also been in Sailor Moon’s pilot, like an Otaku Mandela Effect.  And in turn influenced what High School Anime pilots are “supposed” to be like in their collective subconscious.

I consider this an interesting example of how Sailor Moon has been an influence beyond just the Genre she started or Shoujo in general.

Another example would be how many Teachers in Anime are basically just Miss Haruna, like Miss Yukari in Azumanga Daioh and Mis Kuroi in Lucky Star.

Or heck even Noir which uses it’s Golden Pocket Watch with an Iconic sentimental Melody near the end in exactly the same way, and by a Blond character voiced by the same Seiyu in Japan.