I find that I enjoy imagining fictional characters interacting with Sagan 4. So I'm gonna do that with some Homestuck characters.
In the pre-scratch universe, Sagan 4 ended in April 2009 on the same day Homestuck began because most or all of Sagan 4's members died in the reckoning. It's fun to imagine a potential sburb session played by active members of the time, but that's for a different post. Instead we're focusing on how Sagan 4 differs because of some Homestuck characters interacting with it.
John Egbert has zero interest in Sagan 4 and never considers joining, if he knew about it at all.
Rose Lalonde, at age 11, tried to join at its peak in 2007 by making some absolutely wretched species of ukfauna. She misinterpreted ukfauna anatomy very badly and it was rejected.
Around the same time, Jade Harley also tried to join, unaware that Rose had tried. Jade had more success and made a good number of nodents and shrews throughout 2007, 2008, and early 2009. You know she would.
Dave Strider didn't join Sagan 4, but he knew of it, because his Bro signed up and made several species, including the ugliest sauceback to ever exist. Bro was later banned for toxic behavior, a few weeks before the events of Homestuck.
Rose's Mom probably knew of the project, but didn't contribute.
That's about it.
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In the post-scratch universe, things get more interesting. In this universe, which is closer-aligned with our own, Homestuck begins in 2011, so a lot of major events in Sagan 4 history have already happened.
Jane Crocker is actually a big fan of Sagan 4, but she'd never contribute, she could never do that. Having an interest in frightening fauna, she is fascinated by the species produced in the alienification phase and saddened by the post-snowball resurgence of Earth clones. In other words, it's a good thing she didn't join because she would almost certainly alienify everything to the point of no longer being recognizable or functional. She likes saucebacks, though.
Jake English probably wouldn't have too much of an interest in Sagan 4, at least at first.
Roxy Lalonde would know of it, for certain, but I'll get to that in a little bit.
Then there's Dirk Strider.
Dirk would know of Sagan 4, and of everything that happens after 2011. He has read every single entry that exists or will ever exist on Alpha, Beta, and Gamma. He has made numerous fan species based on all three timelines. Since Sagan 4's flooding event was happening in 2011, either Dirk or Roxy has on at least one occasion tried to use it to explain to Jane what Betty Crocker did to the Earth, with no success.
Wait...what the heck is Sagan 4 Gamma?
Though the post-scratch universe aligns more with ours, things do eventually diverge. In this universe, Homestuck is real instead of a work of fiction. In late 2021, the adult post-scratch version of Rose Lalonde joins Sagan 4 (both Alpha and Beta) under a pseudonym and joins me and Colddigger as a third Monarch of The Cursed, contributing greatly to deep sea ecosystems with each new organism weirder than the last. She became a beloved member, and some years down the line as Sagan 4 had to face the unprecedented threat of its members being killed in the hilarocaust, she vanished. As I was still alive, I tracked her down and learned her real name and that she had been killed after trying to make a stand against Betty Crocker. It was not long after this that Miraheze and Jcink went down for good, rendering Sagan 4 Alpha and Beta inaccessible, though fortunately not without backup.
We few surviving Sagan 4 members banded together to make a Sagan 4 Gamma that was not just a collaborative spec project, but an act of rebellion in Rose's honor. After getting our hands on something like ecto-alchemy equipment stolen from Crockercorp, we were also able to make our submissions real; this included Alpha and Beta species that we still had the data for, as well. Physical manifestations of our artwork helped us defend ourselves against Imperial Drones and whatever else Betty Crocker sent our way as we all gathered at a base of operations atop a mountain unaffected by the water apocalypse--and all surviving Sagan 4 members got to meet in real life, albeit out of necessity for survival. Sagan 4 Gamma rapidly also became a safe haven for people all over the world seeking protection from Betty Crocker's tyranny. It thrived like no version of Sagan 4 ever had before, as it became a sort of symbolic thing for everyone who entered our protection to make a species and there were quite a few creative minds who had survived the genocide and apocalypse thus far.
Sagan 4 Gamma became one of the longest holdouts of humanity free from Betty Crocker's rule, lasting over 150 years after the rest of civilization has fallen. But we, or rather our descendants, couldn't really do much meaningful against her, so she didn't really care after a while and just left us alone. Sagan 4 Gamma became the largest and longest-running spec evo project of all time. But our time was not to last forever. Without a common enemy, our descendants started fighting amongst themselves, and eventually the ecto-alchemy equipment and other stuff they had depended on for food is destroyed. Mass starvation leaves behind a survivor population too small to keep up, and eventually the last members of Sagan 4 Gamma, like the rest of humanity, have died.
A few centuries later, Dirk Strider discovers the project and the backups of Alpha and Beta and decides to start Sagan 4 Delta. It's a seed world with all the best and most iconic species from all 3 timelines.
Of course Roxy is a member. She knows all about Gamma because it was made in her Ancestor's honor, and the idea of contributing and even making descendants of Rose's species?
Jake joins and tries to make the aliens from avatar. Of course he does.
Callie probably contributes some wonderful artwork. I could see her brother Caliborn trying as well. Dirk has no standards so he just approves Caliborn's scribbles, including a diorama where he seems to be attempting to depict a crestgill from Beta in a sexy pose.
Then there's Jane. From her perspective, it's still 2011. She thinks Dirk just made up the limbo, Sagan 4 Beta, the Mason revival, the retcon event, Sagan 4 Gamma, famous author Rose Lalonde of all people being a member, and...really, tamjacks becoming tool users, saucebacks evolving into birds, and those primitive cloney nodents coming back from the dead? There's no way those would ever be approved! But she contributes to Sagan 4 Delta anyway. She turns some saucebacks into Beasts from Problem Sleuth.
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Eventually, the new universe is created and there's Earth C. Both sets of human kids live as Gods on the same planet now. Rose finds out about post-scratch Sagan 4 and about Sagan 4 Delta and is immediately interested. Jade is sad that nothing like her pre-scratch contributions existed after the scratch but also wants to resubmit some of them, now remade and improved, to Delta. Jane wants to make stuff for Delta for the nostalgia, as does Roxy. Dirk is no longer interested in running Delta, but Callie is. Thus the project kicks up again under Callie's management, and before long Alpha, Beta, and Gamma are brought back too, though they mostly get contributed to by mortals while Delta remains the thing of the Gods.
And now the surviving trolls know about it too. All of them make at least one species and Kanaya becomes the project's dedicated "plant guy". Terezi also contributes regularly, making some pretty neat and colorful cursoriopedes, so when she left Earth C and re-entered canon to look for Vriska, it was the loss of a great member.
Over the next 7 years, each Creator contributed to Delta at least once, even those who hadn't had any interest in Sagan 4 in the past like John and Dave. They sometimes contributed to the restarted other 3 timelines as well. Gcatavrosprite manages to make a fairybull out of a pinyuk and it's actually really clever how he does it.
Sagan 4 Alpha reaches the end of its habitable period by the time of the Meat/Candy split, leaving it complete, while Beta, Gamma, and Delta are still ongoing.
This post is getting too long I'll brainstorm what the meat/candy split does another time