Has anyone ever stopped to consider what the original timeline was like, before it was altered by Chibi-Usa and the Black Moon?

As far as I can guess, the following is true:

*Episodes 01-59 are the same. Dark Kingdom and Doom Tree arc happened as we saw them.

*Episodes 60-88/89 didn't happen at all (with the exception of the Usagi/Mamoru scene at the beginning of episode 60). The Senshi didn't receive their new transformation devices or attacks in episode 62. They never met Chibi-Usa, never went to the future, never met Sailor Pluto, and never learned of their future. Usagi and Mamoru never broke up.

*The R theatrical short never happened.

*The R movie happened - but without Chibi-Usa present. Perhaps this is when the Senshi got their new devices and attacks in the original timeline?

*Episodes 90-102 happened as we saw them.

*Episodes 103-127 occurred in an altered form. Obviously, Chibi-Usa never showed up, so all of her plots (and their impact upon the main characters) never happened. Speculation can abound here. How did they meet Hotaru? Was Usagi the one that originally befriended her? Did Pluto originally get in on the action or not?

*The S movie happened - but without Chibi-Usa present.

*Episodes 128-166 must have been very different. Speculation can run rampant here. Obviously, all plots regarding Chibi-Usa never happened. Who got Pegasus, though? Was it Usagi?

*The three-part Super S special occurred in a highly altered form. The first part didn't happen at all. The second part happened as we saw it. The third part probably didn't happen - or maybe someone else discovered Ririca's secret?

*The Super S theatrical short occurred in an altered form.

*The Super S movie might have happened. Maybe? Chibi-Usa was a big part of it. Any guesses?

*Episodes 167-172 occurred in an altered form - without Chibi-Usa present.

*Episodes 173-200 probably happened as we saw them.

Any thoughts on this?

Well the Season R/S Chibiusa did not know Uranus, Neptune, or Saturn so that suggests that one of two things happened.  Either they died (and stayed dead) before Chibiusa was born or they did not become Sailor Moon's allies for some reason.

Of course yeah if we are talking time travel then you have to figure out Pluto's deal first.  In S she has to be either the Pluto of the present or the Pluto of the future.  Given that she knows Small Lady then I lean heavily towards her being Future Pluto.  What does that mean though?  Since Pluto was the one to bring Haruka and Michiru back to life that could mean they permanently died in the original timeline.  That seemingly fits with what I said earlier about Chibiusa not knowing about them in the future.   But then what about the third talisman her Garnet Orb?   It had to be in possession of present Pluto...but we know she can't die or else she would never have become Future Pluto.  So either it was not stored in her heart crystal or else the talismans were not all gathered in the original timeline.   From the art episode we do know that Chibiusa's mother also possess the grail, so that more than likely means that present Pluto must have then gotten involved and already been in possession of the Garnet Rod.  How that went down is anyones guess.  Was she already active at ths time?  Was this her re-awakening as a senshi?  Whatever we just know somehow Sailor Moon ended up with the Grail.

As far as Saturn, honestly I lean towards thinking that Usagi would not have befriended Hotaru like Chibiusa did.  I mean we are talking a pretty sizable age difference, where even if I could see Usagi being nice to her if she ran into her in the park...I don't see her really hanging out with her and taking her places on her own?  Keep in mind that Usagi was also likely matured quite a bit playing mother to Chibiusa in R.  So again would Usagi have really taken on that level of involvement with a strange kid on her own without that?  Even in the final timeline it was usually Chibiusa who always had to ask to include Hotaru in things. 
It was Chibiusa's compassion that played a role in giving Hotaru the strength to awaken Saturn inside of her, and it was Chibiusa's pure heart crystal that allowed Mistress-9 the strength to awaken.  So without Chibiusa's super strong crystal to steal basically I am guessing that Super Sailor Moon the Inners, and Pluto found and defeated the Deathbusters before they could gather enough pure heart crystals to fully awaken Misstress-9.  So then either they cleansed Hotaru of the weakened M9 or she died.   Either way my thinking is that Saturn never awakened and she never actually became friends with the Senshi in the original timeline.)
(So my theory on what happened after is that at first when Chibiusa is sent back in S, that she messes things up because that meant the awakened Misstress-9 with her pure heart crystal but what was still missing was Souichi Tomoe.  He was also vital to get through to Hotaru but he was still possessed by Germatoid in the timeline where Uranus/Neptune were still dead.  So basically I think evil might have initially won when Chibiusa went back alone and thus Crystal Tokyo may have started to fade like in the Stars manga.  NQS would not know what exactly what changed but knowing the time Chibiusa was sent back to train in figured that it was something regarding the awakening of the Messiah of Silence.  That's why she would have sent future Pluto back in time to do everything she could including reviving Uranus and Neptune in order to prevent the Messiah of Silence from rising at all costs.)

S-Movie we are not talking too big of a difference other than Snow Kaguya would have had to be defeated without the power of Uranus/Neptune/MiniMoon in the final attack.  Not a big deal.

For Super S...yeah I'm guessing Helios may have hid out in either Usagi or Mamoru.  I mean he did know them in the past.  I actually lean toward Mamoru since he is the one actually connected with the Golden Crystal in the manga and it is probably also the case in the anime based on him having a golden starseed.  Plus to me with the impressive level of his psychic powers in the future as King Endymion (including power over Dreams!) it suggests to me that he more than likely does possess the Golden Crystal at that time.   Furthermore as I see it following sequence of events if the golden mirror was in Usagi when she was attacked no one would be able to save her and stop it from being taken and her killed, but if it was in Mamoru, Sailor Moon would still be able to rescue him as once they had the mirror they would not have bothered trying to kill him since he would not have seemed like a threat.  Either way with the mirror in Usagi or Mamoru that means it would have been found before they met and befriended the Amazoness Quartet.  Which once again explains why Chibiusa again would not know them in the future.  Anyways endgame would have then been a resolution much closer to the manga of Mamoru wielding the Gold and Usagi the Silver that would have ultimately sealed Nehellenia.

Super-S Movie yeah I have no clue.  I mean for starters it was Diana who woke up Usagi to let her know all the kids were leaving.  And it was seemingly Usagi who paged the other Senshi.  Otherwise they would have seemingly only learned about the mass kidnapping in the city the next day and would have no clue where to look.  It was Chibiusa who befriended Perle and made him question his beliefs and later her cookie that gave further strength.  It was Chibiusa who provided Queen Badiane with enough power to complete her black dream hole.  She also played a role in Usagi being able to snap out of her induced dream state...  So yeah I have not the slightest clue where to begin to guess how events could have played out here but they were drastically different or else Queen B was time traveler herself so it didn't happen in the original timeline at all...

Without Uranus, Neptune, and Saturn (and also no Mini Moon...although she was not part of it in the manga was she?), Usagi couldn't have become Eternal Sailor Moon in Stars.  Although would that have been a big difference?  I mean I guess she would have just had to use her Princess Serenity winged form to fly to Nehellenia.  Besides that though maybe Rainbow Moon Heartache or tapping into the Silver Crystals power directly could have been strong enough to cure the fake senshi until ChibiChibi upgraded her?   In the Galaxia fight she didn't do much of anything besides use the Silver Crystal's power directly (a failed Power Kiss could have been any attack).  Other than that without the Xenophobia of Haruka/Michiru an alliance would have probably  been formed between the Inners and Sailor Star Lights sooner.  I mean Sailor Moon was about to shake Seiya's hand to symbolize it when they interrupted.  So information would have been shared sooner but I'm not sure that would have really made much difference.  The Sailor Moon Galaxia fight would have likely gone down essentially the same just without the angst of watching Uranus/Neptune get killed in front of her.

^Wow, that's impressive!

I don't mean to take the wind out of your sails, but I always thought Neo-Queen Serenity knew her daughter would have to be sent back to stop the eventual Black Moon attack. However, that gets into the murky territory of whether she could have used the knowledge gleaned from being with Chibiusa in the 20th century to stop the rise of the Black Moon in the first place........
Tis a bit headache inducing.

One theory I've heard before which I found interesting is that as Sailor Moon fights enemies, she (and the Silver Crystal) gain, or at least release, more power. This power or light attracts other enemies like moths, they fight her, she gains more power attracting even more enemies, and the cycle continues.

With this theory, in the original timeline where the first Chibiusa was born, after the Dark Kingdom, with no Black Moon Clan, Sailor Moon doesn't level up and the Silver Crystal is not bright enough to attract the Death Busters from the Tau Star System. You could continue this reasoning to say that there were no more enemies, happily ever after, but I think it's more likely there was some form of enemy attack that led Neo Queen Serenity to take the throne. 

The most likely candidate is Nehelania. She still has motives to attack and let's be honest Galaxia would decimate a post-season 1 team with no outers and no starlights. Anyways, in the manga the "maiden" Helios was looking for was actually Usagi instead of Chibiusa, so this could still be consistent with the no-time-travel. Obviously a Dream arc would look entirely different with no outers there to fight, and it could have escalated to the point of global mass destruction, where Sailor Moon felt her only choice was to become Neo Queen Serenity, restore the world and banish/destroy Nehelania (this is where I imagine the Holy Grail comes in). After the immediate threat had dissipated, this is a time where it would be logical for Usagi to take position and Ruler of the World to help rebuild the world. (I feel as though she must have become queen through a consensus of the people, as she doesn't seem like the type to declare and enforce such things on her own.) Even if she did have a majority consensus, it still wouldn't be unanimous, leading to groups such as the Black Moon Clan. The final burst of energy used to seal/destroy Nehelania could have also awoken Death Phantom, allowing him to take advantage of such groups. The Black Moon Clan travels to the past, so does Chibiusa, and everything changes.

The second Chibiusa (during the Infinity arc) is a Chibiusa born from the universe where 1 Chibiusa went back in time and the Black Moon Clan was stopped, but then time travel shenanigans ended. The Death Busters most likely still attacked in this universe, so the outers were still awoken, but with Chibiusa absent, the situation with Hotaru might have gone very differently, the outers might have even succeeded in killing her. I don't believe this Chibiusa knows about the outers either, so I imagine they either died or ended up taking their posts on their planets (or at the gate of time or whatever Pluto does). While the latter seems odd, I think it's a thing they might do if they killed Hotaru, as they would still be concerned about the talismans resonating and awakening Saturn. Of course, there's also the option Usagi befriended Hotaru and everything went great, but as mentioned above, that's a bit unlikely.

I'm not going to get into the alternative worlds that the Dream and Stars Chibiusas might have come from because this is getting a bit excessive and also I don't remember the Dream arc that well. Also while I super love this theory, I will admit it does contradict a few things, particularly the whole "Chibiusa is disappearing because Mamoru died" point... if she came from a different universe, she wouldn't be affected by this Mamoru dying!

Honestly, I always thought of it as a continuous loop, so Chibi-usa always goes into the past. The only reason why I thought this was because so many important events rely on her. But your theory is very good!