Animaniacs had a large cast of characters, separated into individual segments, with each pair or set of characters acting in its own plot. The Warner kids, Yakko, Wakko, and Dot, are three 1930s cartoon stars of an unknown species (one Tom Ruegger named "Cartoonus characterus") that were locked away in the Warner Bros. Water Tower until the 1990s, when they escaped. After their escape, they often interacted with Warner Bros. studio workers, including Ralph the Security Guard; Dr. Otto Scratchansniff, the studio psychiatrist, and his assistant Hello Nurse. Pinky and the Brain are two genetically altered laboratory mice who continuously plot and attempt to take over the world. Slappy Squirrel is an octogenarian cartoon star who can easily outwit antagonists and uses her wiles to educate her nephew, Skippy Squirrel, about cartoon techniques. Additional principal characters included three pigeons known as The Goodfeathers, Buttons and Mindy, Chicken Boo, Flavio and Marita (The Hip Hippos) and Katie Ka-Boom. Exclusive to the first season, Rita and Runt, two strays that get into massive trouble and adventures, starred in their own segment.