Before that, Shredder and Krang come up with a plan that finally lets them get ahead of the turtles: They trap April and one of the four in an airtight bank vault, so that while the remaining turtles are trying to rescue their trapped friends, Bebop and Rocksteady are able to get ahold of a power source they were needing. It's one of the few times that Shredder and Krang are able to successfully trick the turtles and get exactly what they needed.
In the episode "Son of Return of the Fly II", the Turtles are all tied into death traps by Baxter Stockman, using hard light ropes to keep them in place. Leonardo pulls a small knife from his wrist strap and starts cutting. As the traps are all about to go off, Raphael asks Donatello if he can get out. Donatello tells him that only the most skilled ninja master could escape the ropes. Cue Leonardo leaping from his death trap with sword drawn, freeing his brothers as the theme song plays. What completes it is Donatello's pleasant "Oh, hi Leonardo."
The turtles first scene in the show; they save April from street punk assassins while remaining hidden in the shadows.
The episode where the Technodrome invades New York and Krang plans to draw the whole earth into Dimension X...the Turtles get around the forcefield when Donatello "borrows" an army vehicle, blasts his way underground, and shoots a missile directly UNDER the Technodrome. The missile carries off the giant mobile fortress and sends it through the portal first...where Krang's Stone Warriors, ready to attack the planet, start firing as soon as they see something coming through. The Technodrome is utterly decimated by artillery fire and crash-lands in Dimension X, trapping the bad guys there. The aftermath is even better as the forever-persecuted Turtles finally get a hero's reception from the citizens of New York for their efforts.
Master Splinter kicking Shredder's ass in "Blast from the Past"...with The Three Stooges gags.
Leonardo gets on in "Hot Rodding Teenagers from Dimension X". The turtles are in a flying car and find the weather machine that's causing havoc. Leonardo leaps out of the car and slices it in half with his katana. Had they not had a flying car, he would have died saving the city.
Raphael: Everybody complains about the weather, but you actually did something about it.
In one episode, a mugger approaches the turtles.
Mugger: Gimme your wallet.
Leonardo: I got a better idea. (pulls out his katana) You give me your knife.