CATS are the main antagonists from Zero Wing.
Story
CATS is a group of Space Pirates operating around the Milky Way and Andromeda. In 2101 AD, The Galactic Space Federation starts the "Galaxy Defense Base Development Plan" to build eight defense bases to protect the galaxy from invasion. Behind the scenes, however, the Federation was setting its sights on conquering the Andromeda galaxy, so they stroke a deal with CATS to help them in their conquest.
Two years later, after the completion of the bases, the Federation sends a group of military carriers to the completed defense bases. However, they are promptly blown up by CATS, who betrays the Federation and takes over all of the bases. Before being destroyed, one of the carriers manages to launch a ZIG-01 spacefighter, who is given the mission of fighting back CATS and taking back the bases from them.