Some TMNT stuff really isn't for little kids.
Chang Lee is a Chinese martial artist who befriends the turtles after they defend his uncle Hu-Shang's restaurant from a group of Beancurd's thugs. He is one of many homages/parodies of Bruce Lee in the TMNT franchise.
Unsavory spice merchant Beancurd sends off his minions to trash Hu-Shang's Restaurant & Takeout, as Hu-Shang refuses to use the cheap spices and frozen foods that he and his business partner Gorko have muscled the other restaurants in the city into peddling. The turtles had just arrived at Hu-Shang's for something to eat, and take the thugs out.
Just as they are fleeing, Hu-Shang's nephew, Chang Lee returns from a study program. After Hu-Shang tells him that they fought them off, Chang offers to feed the turtles as honored guests.
As they polish off their meal, Beancurd himself arrives with a trio of enforcers - Bugsy, Pretty Boy Bob, and Ching Lo Lefty - to continue attempting to bend the restaurateur to his will. Chang easily takes out all three of them and insists that the miscreants leave immediately.
Beancurd goes begging back to Gorko, who has a final solution - a massive mountain of muscle by the name of Buff Nordick. Gorko sends for Nordick to begin his final assault.
The next morning, the turtles arrive at Hu-Shang's to find it burning to the ground. Chang Lee had dropped his uncle off at his brother's home to stay for a few days and swung by to pick up some groceries before returning to the restaurant and finding it naught but kindle. The turtles help Chang rebuild the restaurant, then set off to settle the score once and for all.
Gorko sics some more henchmen on the turtles and Chang, but they make easy work of them. Buff arrives and Chang fights him. Buff picks up a mace flail at one point and cuts Chang open, but Michelangelo picks a sansetsukon off of the wall and hands it to Chang, allowing him to defend against the flail and get the advantage over Nordick, eventually choking him into unconsciousness.
Later, the turtles and Chang down chow down again, and laugh at the fact that now their antagonists are now conscripted into helping around the restaurant.