The People's Choice: Out camping for the night, the four turtles find themselves in the middle of an election. It's not any ordinary election. The two female candidates are from a distant planet where the political process is trial by combat.
Sons of the Silent Age: Taking a Huck Finn styled trip down a local river, the turtles, Casey and April discover a nuclear power plant ... as well as mermen of Y'Lantias ... the last of their kind.
Wing and a Prayer: It's a bird! It's a plane! Okay, it's this guy with angel wings, an Avian, named Raptarr who is after this other guy with metal wings, named Mephos, who wants to take over the Avians' flying city.
Leonardo goes with Casey to put an end to Hun's plans to bring the Purple Dragons to glory. But can both control their anger and succeed in their mission?
The Ancient One: It is time for Leonardo to move on. Splinter sends Leo to a new sensei ... or rather, a very old sensei. The journey is long and perilous. Can Leonardo look into himself and find the right answers to his questions?
While Leonardo trains with the Ancient One in Japan, Karai goes after the remaining Turtles and Splinter who must defend their home from Foot Ninja without Leo's help.
Outbreak: Something is growing and spreading in the sewers and the waterways.The remnants of Bishop's 'aliens' have infected various animals, mutating them into horrible beasts ravenous for anything that gets in their way... including turtles.
Stockman finally succeeds in cloning himself a new body, or so he thinks. Something has gone horribly wrong and his new body soon begins to decay. Losing both his mind and body, Stockman goes after April O'Neil in revenge.
The Return of Savanti Romero: Part 1: Evil demon sorcerer Savanti Romero is back! Back in time, that is - he's stuck in the Jurassic period, but is causing trouble for the Turtles in the present day.
The Return of Savanti Romero: Part 2: Evil demon sorcerer Savanti Romero has lured the Turtles back to the Jurassic period to exact his revenge, as well as get his hands on the Time Sceptre.
The turtles are cleaning up their new lair. Donatello shorts out a circuit breaker. Michelangelo begins to flip out, but Splinter suggests telling stories. Leo relays a story that the Ancient One told him at the end of S4E14.
Donatello starts to undergo a horrifying mutation after his previous encounter with Bishop's mutants. The Turtles place him in April and Casey's care but unknowingly put the pair in danger.
The TMNT return to New York to retrieve a pendant that Bishop wants in exchange for Donatello's cure. And it's under the ownership of the New Shredder, Karai.
The turtles are sick of being stuck inside their lair and decide to go out and enjoy the night, but they are approached by strange warriors who make the night a little more interesting.