This is the first episode where Mikey uses a man-riki-gusari, a chained weapon. His nunchaku would be phased out altogether after the first few seasons.
First appearance of what would later become the Turtle Van.
Shredder uses special Transport Module-like drilling devices which enable the Foot to travel from the Technodrome to city level, however these would never be used again and would be replaced by the more familiar model used in the third, fifth and sixth seasons.
This is the first appearance of Baxter Stockman and the Mousers. Notably, Stockman is depicted as Caucasian here despite being African American in other TMNT related media.
The Turtles meet Krang for the first time.