The first episode of the 2003 Teenage Mutant Ninja Turtles animated series is titled “Things Change.”
The episode introduces the turtles’ underground home, their training with Splinter, and their first major encounter with the Foot Clan. It establishes the series’ more serious tone and its emphasis on discipline, family, and the consequences of living secretly beneath New York City.
“Things Change” originally aired on February 8, 2003, as part of the series premiere. The 2003 show was developed for Fox’s Saturday-morning programming and drew heavily from the darker atmosphere of the Mirage comics. Its first season later expanded the mythology through characters such as the Shredder, Hun, and the Utroms.