(Based on various sources in the show)
Savanti Romero is banished to live amongst the dinosaurs, but soon causes enough trouble to get Renet involved, who brings the Turtles along with her. They defeat Savanti but spend 3 months searching for the Time Scepter before they can return to their time.
An evil being known as The Shredder terroizes Japan and Emperor Ōjin sends an elite group of warriors called The Five Dragons to destroy him. Their greatest warrior, the original Oroku Saki, appears to kill the demon, but instead they fuse together.
After a reign of terror, Oroku Saki/The Shredder is defeated by what remains of The Five Dragons and is imprisoned for eternity.
The Utrom crashland on Earth and set up base in Japan.
Ch’rell takes up the identity of The Shredder and re-establishes the Foot Clan. Since they are being hunted, The Utrom recruit honorable warriors to serve as Guardians and protect them.
Ch’rell eventually uses a magical amulet known as The Heart of Tengu to mystically enslave The Demon Shredder’s heralds and uses them as his own personal mystic warriors.
Ch’rell (as Oroku Saki/The Shredder) brings the Tokugawa Shogunate to power in Japan, starting the Edo period.
January 8, 1815
American soldier John Bishop (in his original body) is abducted by aliens during The Battle of New Orleans. Although he goes through painful tests, his body is gifted with extremely advanced longevity. This sparks his hatred for aliens.
President Ulysses S. Grant establishes the Earth Protection Force. Agent Bishop is placed in charge.
Agent Bishop accquires an alien space ship and a test subject in Roswell, New Mexico.
Hamato Yoshi is born.
A young Yoshi is taken in by The Ancient One.
Yukio Mashimi betrays Yoshi and the Utroms by murdering Tang Shen and revealing the Utroms’ hidden base and many secrets. They are forced to flee to NYC after being attacked by Shredder and The Foot. Yoshi kills Mashimi in a duel.
Yoshi seeks the Ninja Tribunal’s aide in battling The Shredder. They refuse, since he is merely an imposter of the original Shredder.
The Shredder most likely adopts Karai around this time.
Casey Jones is born.
April O’neil is born.
Purple Dragons burn down the Jones Family’s store. Casey’s father is killed by Hun.
Hamato Yoshi is finally tracked down and killed by The Shredder.
Splinter and the Turtles are doused in mutagen after an accident involving a TCRI truck.
Splinter takes the Turtles to Japan to visit The Ancient One and spread Master Yoshi’s ashes.
Splinter begins training the Turtles in the art of ninjutsu.
Serling accidentally appears through a time portal and is claimed by the Turtles as their new toy since he’s been shrunken down to mere inches. He eventually returns to 2007.
The Turtles meet a boy named Arnie (actually Casey Jones) and proceed to train him so he can deal with neighborhood bullies. Michelangelo inadvertently leads him to coin his battlecry: ”Goongala!”
Splinter teaches Leonardo to overcome his fear of heights. Leonardo and Raphael fight a giant albino crocodile. Leonardo saves Donatello from large amounts of sewer garbage. Michelangelo tries to make Leonardo crack a smile while he’s perfecting his kata.
Splinter wins The Battle Nexus tournament. He is later ambushed by his opponent Drako but is saved by Miyamoto Usagi.
The Turtles turn 15.
The Turtles are forced from their home by mouser robots and their feud with the Foot clan begins. They meet long-time friends April O’neil and Casey Jones.
The Turtles confront The Shredder for the first time. They are overmatched and get split up during the skirmish, but face him again later that night. He is defeated by Splinter, but survives.
Shredder attacks the Turtles full-force, destroying April’s home in the process. They flee NYC with April and Casey, all believed dead by the Foot Clan.
The Turtles ”Return to New York” after spending the winter hiding in Massachusets. Leonardo decapitates The Shredder with the Sword of Tengu and Donatello disables most of the remaining equipment in the Foot Clan’s tower. Master Splinter goes missing after being injured in the battle.
The Turtles inflitrate the TCRI building looking for Splinter. They are accidentally transported across the galaxy and meet the Fugitoid, who is on the run from The Fedaration and Triceraton Republic due to his knowledge of a transmat device.
The Turtles and Fugitoid return to Earth after evading the warring aliens, the TCRI bulding is attacked by The Shredder. The Utrom flee to their homeworld and the Shredder (who is revealed to be an Utrom) is left in the imploding building, he is assumed dead.
The Turtles Turn 16.
With The Shredder gone, the city’s gangs are at war. Karai, head of the Japanese Foot and daughter of The Shredder, allies herself with the Turtles to put an end to the chaos. A truce is made between the Foot and the TMNT.
The Shredder once again emerges from his apparent death and breaks the truce, putting Karai at conflict between her honor and her duty.
Michelangelo wins the Battle Nexus Championship after a controversial victory over Kluh from planet Levram.
A Christmas feast is held at the TMNT’s lair. Michelangelo adopts Klunk.
The Triceratons invade Earth in seach of the Fugitoid. The Turtles encounter Agent Bishop for the first time. The Fugitoid cripples both the Triceraton Republic and The Federation by uploading a virus into their systems. Traximus overthrows the current Triceraton regime and brings peace between them and the Federation.
The Turtles turn 17.
The Shredder builds a star-ship from salvaged Triceraton technology, the Turtles nearly die trying to stop him, but they are saved at the last second by the Utrom. He is found guilty by the Utrom and is sentenced to life on Mor Gal Tal, an icy space asteroid. Karai vows vengeance.
The Turtles and Splinter recover from their battle in Northhampton, Massachusetts. They come back to New York fully healed, but Leonardo can not get over his failure.
Splinter sends Leonardo to seek the Ancient One after realizing that there’s nothing more he can do for his troubled son.
Karai assumes the mantle of The Shredder. She attacks and destroys the Turtle’s home while Leonardo is in Japan training with The Ancient One.
The Turtles battle a mutant outbreak caused by Agent Bishop. Donatello is unknowingly infected and mutates further some time later.
The Turtles rescue a mutated Donatello by retreiving the Heart of Tengu for Bishop, who is tricked into destroying it, thus releasing The Shredder’s Heralds (the Foot Mystics).
The Turtles train with 4 other accolytes under the Ninja Tribunal and eventually battle the ressurected Demon Shredder. The spirit of Hamato Yoshi destroys him for good. Karai lets go of her vendetta against the Turtles.
The Turtles turn 18 some time during the ”Ninja Tribunal” events.
The Turtles are sucked into the future by Cody Jones.
The Turtles turn 19 while trapped in the future.
The Turtles return to from the future and spend months battling the new Cyber Shredder and recovering Splinter’s data bits. April and Casey are married at ages 27 and 28, respectively.
Serling is sent back to the future.
Presumably, the Turtles and Splinter return to The Battle Nexus for another tournament. The winner is unknown.
The Turtles meet their Original Cartoon and Mirage comic-book counterparts and defeat Ch’rell once and for all before he destroys the multi-verse. Hun is turned into a mutant Turtle.
The Turtles turn 20.
Bishop and Stockman’s alien lab is destroyed by accident but Bishop is rescued by one of his alien prisoners. Although Stockman is left for dead, Bishop goes on to change his ways and become president of the Pan Galactic Alliance.
Cody Jones is born.
The Turtles and Splinter appear in the future and meet April and Casey’s great-grandson Cody Jones, as well as his robot companion Serling. They battle many new enemies, mainly Sh’oKanabo, and discover that Bishop is now a world leader who fights for peace and harmony.
The Turtles ascend to the ninja rank of Chunin.
The Turtles, along with Splinter, Cody, and Bishop, kill Sh’oKanabo and seemingly delete Viral, ending any threat of the Day of Awakening for good.
Presumably, all the loose ends of Fast Forward are tied up. Including what happens to the Dark Turtles. Cody sends the Turtles back to their time. There is a malfunction caused by Viral, and Serling is accidentally sent back too. Luckily, Cody gets the time machine working again on his own some time later.