Dave Filoni and Henry Gilroy were developing the carbon-freezing tactic while preparing the first season. Gilroy used it in a Dark Horse Clone Wars comic, The Shipyards of Doom, before Filoni got to show it on screen.
First appearance of Tarkin, who is still a captain on the good side here, but will eventually become one of the Empire's governors, and a main antagonist in Star Wars: Episode IV - A New Hope (1977).
K2-B4 was voiced by Ashley Eckstein, who also provided the voice of Ahsoka Tano in the series. K2-B4's name is a reference to basketball player Kobe Bryant, who wore the jersey number 24 during the latter part of his career. Her color scheme of purple and gold matches that of the Los Angeles Lakers, who Bryant played his entire career for. These references were included by Lakers fans on the crew of The Clone Wars, as the Lakers won the NBA championship during production of "The Citadel". From Wookiepedia of K2-B4
It's the first time a clone trooper with phase II helmet is seen in the series (more specifically a clone trooper of 501st legion).