When the Turtles are crossing the tightrope after April and Casey got into the TCRI building, Leonardo is leading the walk at the beginning. However, when the Turtles get off the rope, Donatello is in front. Since there is no way the Turtles could have switched positions while up several stories in the air, this is definitely an animation frame mistake.
Donatello isn't holding the pigeon puppet close enough to the camera, as it's not occupying the camera's entire field of vision. The TCRI security guard should have been able to see Leonardo placing the background photograph behind the pigeon.
In the beginning April is wearing a yellow shirt, later on she is wearing the same clothes from "Tales of Leo".
Episode centers around Raph.
The reporter had captured some gangs on film which was going to shut them down. In the original series, this is what April O'Neil did, and a gang came after her too.
If Stockman's rocket launcher is strong enough to blow a hole in the floor it should have been strong enough to kill the Elite Guard when he fired it directly at them.
Leonardo has three fingers. Yet the glove has more fingerholes than Leonardo has fingers. Yet he is able to wield the Sword of Tengu with the glove worn on his hand. Even if he could wear such a heavy glove with not enough fingers, he couldn't wield the sword so skillfully.
Stockman's body is a marvel of technology, because each of its four arms has multiple functions: a machinegun, a rocket launcher, and a flamethrower. At any given time, he can use any ammunition. This way, Stockman has the element of surprise.
This is the first time we see Splinter without his ninja robes.
How did Mikey have the shell cell in his belt? the first shot, it wasn't there, but in the next shot, it is there.
When Donatello was typing in the code to get into the Turtles' lair, it sounded like the main theme song.
How did Donatello know what the Foot Tech Ninja were called? The Turtles had met them before, but they had to make a lucky guess to know to refer to them as "Foot Tech Ninja."
The turtles are walking around in the snow without any clothing. Shouldn't they be cold, especially since they're cold-blooded? Walking around in snow without protection would result in hypothermia.
Casey "hangs out" with Michelangelo and Donatello in this episode instead of usually hanging out with Raphael.
Leonardo must have blacksmithing skills, because without any of his katanas left (Shredder threw the pieces over a roof), he had to start from scratch.
In the worst case scenario, the liquid nitrogen would have shattered Donatello's leg when he kicked the door. At the very least, he would have suffered temporary paralysis of his leg and not been able to get very far.
First time in this series that Leonardo was shown using his brother's weapon. In this instance, it's Michelangelo's nunchakus.
Baxter came back after an absence with a new look. He has an eyepatch, a robotic arm, and he's in a wheelchair because of the incident when he failed Shredder in The Way of Invisibility.
The red ribbon that a Mouser picks up and gives to Baxter turns out to be the ribbon that Raph ties to his sais.
Wouldn't the ribbon the mouser found be burned into ashed. Everything was burned down, how could something that small and flammable not be burned?