I'm guessing there's not a whole lot of time between the Paper Marios.
Jr. Troopa certainly doesn't look much older. In her TTYD cameo, Lady Bow says it's been "ages" since PM, but she says she's spent the whole time inside, so just a year or two would seem like ages, and also maybe she has a crush on Mario like every other female character ever in the paper games so she really misses him but a relationship between a Boo and a human would just be too... taboo. They're both in the month of ☆, so it has to be at least a year (there's certainly more than a week between them). Maybe just a year. I'm gonna replay PM to try and get a feel for it, though.
I'd say there's probably not much more than a year between TTYD and SPM, as Luigi comments at the beginning that it's been quiet lately, and Mario has pictures of the PM and TTYD partners on the table behind them, so they're both still fresh in their memories. My SPM disc doesn't work anymore, though, so I'm gonna have to rebuy it sometime.
PM is basically a direct sequel to SMRPG and seems pretty shortly afterward. It probably took more than four months for Bowser to rebuild his castle, though, so I'd put it in the year before. I'm guessing he got the idea for the whole flying castle thing when he saw that Shy Guy in the Clown Copter while he was repairing stuff.
So, tentative timeline outline, without even anything made up, and assuming one year between each game (birth years could be a year earlier if the characters hadn't had their birthdays yet in TTYD):
(SPOILERS!)
(Seriously, spoilers, guys.)
c. 1374 BF:
Creation of the PixlsOne of the Ancients, known as "the master magician," loses his wife and son in an accident. Shortly thereafter, his daughter contracts a deadly illness and dies at a young age. The master magician uses the Dark Prognosticus to create the Pixl Queen, the first ever Pixl (An apprentice of his later claims that the Pixl Queen's soul was that of the magician's daughter). The magician then continues to make eleven more Pixls (the ones, other than Tippi, that you get in SPM).
In the millennium between c. 1374 BF and c. 374 BF, the Tribe of Ancients use the Pixls to build up their civilization, and then to create whole new worlds (This may include the Mushroom World; it is not clear how many worlds existed before this, if any).
c. 374 BF:
The Pixl UprisingThe Pixl Queen uses her mind-control powers to lead her people in a revolt against their masters, and the Ancients are conquered and enslaved by the Pixls. The inheritors of the original twelve Pixls fight back, capturing the Pixls in Catch Cards and healing them. The last surviving inheritor makes his way to the Pixl Queen's castle, where one of his Pixls sacrifices himself to defeat the Queen. The survivor takes the Dark Prognosticus and runs away with it, likely being the founder the Tribe of Darkness. The Ancients limit the powers and intelligence of the Pixls, leading to the slow decline of their once great civilization, the secret of Pixl creation fading into obscurity with them.
FY 1: King Croacus I, the Iron Rose, forms the Flora Kingdom.
c. 126: The eleven original Pixls are stuffed into chests. The Ancients Merlumina and Merlee, and Prince Squirp Korogaline Squipinia of Squirpia, are put into hibernation, holding Pure Hearts to give to the prophesied Heroes of Light. Another Heart is entrusted to King Croacus.
444: King Croacus I's son wilts, sending him into a deep depression and rage, beginning the time known as The Darkening. During this time, he imprisons his daughter for criticizing his policies.
496: King Croacus I is overthrown, probably resulting in his
death wilting. His daughter is released from prison and crowned Queen Croacus II, beginning a progressive rein of kingdom-wide reform.
Before 625: The Luff Empire uses the power of the Marvelous Compass to rule much of the Mushroom World. Their greed dooms them, and the compass curses them for it, bringing their empire to collapse.
A great city flourished on the site where Rogueport now stands. Suddenly, the Shadow Queen, a great demon, destroys the city in a day, sinking it below ground and making it her lair, where she keeps ill-gotten treasures from all across the world. To solidify her reign, she creates the Crystal Stars, placing one in a castle in each country of the continent, and also creates a deep dungeon filled with monsters in which to cast all those who fall into disfavor with her. Among other beasts, her three pet dragons live there.
Cortez the pirate terrorizes the high seas.
625:
The Four Heroes -- the strong, shy Toad boy from Petal Meadows, the wise Goomba girl from the Boggly Woods, the stalwart nomadic Koopa, and the magical Boo who loved him -- seal away the Shadow Queen using the power of the Crystal Stars. However, she is able to place a curse on the heroes that will imprison them in impenetrable black chests when they let go of the stars. Knowing that the seal would one day weaken, they create a map that would lead to each star, and seal it in a box that could only be opened by one with a pure heart (not the capitalized kind). The Goomba hollows out the Great Tree to give the Punies a place to live before she is sealed away.
1297: Worried that having too many children would lead to a violent struggle for the throne, Queen Croacus II chooses to have her only child, a son, this year. He is born with a disease making him weak and sickly.
1298: Queen Croacus II wilts, putting her 1-year-old son in charge of the kingdom. A regent rules in his place for the time being.
1333 (or 34): King Croacus III releases a compilation of his poetry.
1385: King Croacus III wilts, with no
blood chlorophyll heirs. The cause of his death is never made public; many suspect conspiracy. The regent who had ruled in his place is crowned as King Croacus IV.
1560: The First Annual Quirk Quiz is held.
1565: Toadsworth is born.
1570: Zess T. is born.
c. 1595: Mr. Hoggle sets up his Hot Dog Stand in Glitzville.
1597: Goomfrey is born.
1600: Flavio is born.
c. 1604: Goombella is born (assuming she was about 18 when she started college).
1607: Laki is born.
1615: Koops's dad is eaten by Hooktail.
1620: The Pianta changer is set up (it's not clear whether the Pianta Parlor existed before this).
1622: Assuming that the school year at the University of Goom resembles the American one (and that Goombella advanced through college at a normal rate), Goombella enrolls this fall.
1623:
Super Mario RPG: Bowser kidnaps Peach, which he has done at least once, probably multiple times, before. As Mario is rescuing her, the castle is attacked by a sword from another dimension. On its way here, the sword passed through Star Haven and broke the Star Road, scattering the seven Star Spirits across the world. A Star Kid named ♥♪!? descends from Star Haven and takes the form of a wood-carved doll to save the Star Spirits. He joins forces with Mario to repair the Star Road. Humiliated, Bowser must also team up with Mario, to get the sword removed. Once they have done so, they part ways, and Bowser begins repairing his castle. While repairing it, he sees a Shy Guy riding in a Clown Copter (
likely, though not necessarily, placing this after SMW, which would in turn place it after SMB3, which would in turn place it after SMB1 (going against the placement of SMRPG after SMW is that Mario told Geno he had never heard of the Star Road when he could have gone there in SMW, but this can be chalked up to mistranslation or just Mario not seeing the level names on the map screen like we do, or at least that he was there but didn't know what it was)), and gets an idea.
Goombella is a freshman at U Goom in the month of ☆.
1624:
Paper Mario: Having learned of the powers of the Star Road, Bowser finds a way in (perhaps while staying in his
Neon Coney Island Disco Palace castle in the Valley of Bowser during renovations at the main castle, he stumbled upon the Star Road warp right next door) and manages to steal the all-powerful Star Rod. While Peach is throwing a party to celebrate the saving of the world, Bowser's repaired and upgraded castle burrows up through the ground underneath Peach's castle, and carries it up to low-earth orbit. With the power of the Star Spirits, a Star Kid named Twink, and Peach's
prayers wishes, Mario is able to defeat him.
Goombella takes Frankly's archaeology class, probably in the second semester of her sophmore year, though possibly the first year of her junior year (she said she took it "last year," which likely refers to both calendar and academic year).
Some time before 1625: Beldam comes into possession of the box holding the Magical Map, but, lacking a pure heart, she is unable to open its seal.
1625:
The Thousand-Year Door: Peach decides it's high time she and Mario tried taking a vacation again. She happens to stumble upon the X-Nauts as they are obliviously in the process of attempting to open the Thousand-Year Door (at the behest of the Shadow Spirit Beldam, who was a friend of the Shadow Queen back in the day). Beldam, disguised as a merchant, kidnaps Peach after she successfully opens the box holding the Magical Map, intending to use her as the vessel for the Shadow Queen's resurrection. The Crystal Stars get collected, the Thousand-Year Door is opened, and the Shadow Queen possesses Peach, but then Mario jumps on her and things are all better.
King Croacus IV, his mind compromised by the pollution in the water, devises a method for brainwashing the Cragnons. Goombella is a junior at U Goom in the month of ☆.
1626:
Super Paper Mario: King Croacus IV begins his initiative to enslave the Cragnons. Lots of other stuff happens. Existence almost ends.
Goombella is a senior at U Goom, and probably graduates in the Class of '26.
Was the Mushroom World (or the entire Grand Finale Galaxy, or even the whole Mushroom Universe (are the "worlds" that the Ancients created planets, universes, dimensions, or what?)) one of the worlds that was created three thousand years ago? Where does the Star Rod figure into the Mushroom World's creation? Also, how the heck did Bowser get into Star Haven in the beginning of PM anyway? Canonically, the way it happened was that he taped a picture of Kammy onto the book that the narrator was reading from, changing the story. What was the story originally going to be about if not about Bowser stealing the Star Rod and Mario getting it back? Probably would've been a boring story.
It's also possible that the "changing the story" thing means the Paper series is in an alternate timeline. Which wouldn't necessarily make its backstory untrue anyway.
Later I'm gonna try to work out all the months and days that the games happened too.