Running at a mere 11 minutes per episode (before commercials), the show relies more on the comedic - and bizarre - interplay between the characters than on traditional plot devices or ongoing themes. In fact, characters are often killed off in one episode or have their home completely destroyed, only to begin the next episode as if nothing had happened.

Master Shake (or simply "Shake"), whose exploits are often the centerpiece of episodes, is a mean-spirited, abrasive and self-centered white cup with a pink straw sticking out of his lid and two yellow gloves for hands. He takes satisfaction from tormenting the simpleminded Meatwad, and when not hatching schemes he spends his time lazily watching television. He routinely makes irresponsible decisions and is a bad influence on others, especially Meatwad.

Assuming the role of straight man and resident scientific whiz, the large red box of french fries called Frylock provides a stark contrast to the show's many zany and ridiculous characters. In appearance, he sports a goatee, has french fries for hair, and has a blue jewel embedded in his back. Frylock moves by levitation and can shoot a number of superpowered beams from his eyes - including lasers, fireballs, ice-beams, lightning, and flame retardant foam. He uses his fries as appendages in place of arms and hands. When things get out of hand, it is usually Frylock who attempts to get things back under control.

The last member of the household is Meatwad - a chronically stupid wad of hamburger meat with an unnerving talent for deadpan sarcasm. Simpleminded and gullible, Meatwad is easily influenced by the show's many unscrupulous characters. He has a number of makeshift dolls that only he and the audience can hear speak: Vanessa (an apple), Dewey (a discarded paper towel roll), and Boxy Brown (an afro-wearing cardboard box with an attitude). He also has a fixation with a dead pet he calls Squirrely.

Other regulars on the show include next door neighbor Carl Brutananadilewski, a balding, overweight, middle-aged player wannabe who is usually sporting a gold chain, white tank top, sweatpants and sandals. At first glace Carl portrays the image of a hard-nosed badass, but this is largely a product of his accent. In fact, Carl couldn't get a date to save his life, and his sports car with the license plate "2 Wycked" only confirms his desperation to be "happening." Carl and his possessions repeatedly take the destructive brunt of the Aqua Teens' (usually Master Shake's) actions.

Fan favorites, Ignignokt and Err (The Mooninites), are two-dimensional (who claim to be 5,000-dimensional) inhabitants of the Moon. Blockily animated and originally conceived as Atari 2600 era video game characters, the two believe they are far in advance of Earth's culture, but really they're about 18 years behind. Ignignokt, the leader, speaks pompously with an overconfident, snobbish and over-eloquent air. His hyperactive and trash-talking tagalong Err serves as his gopher and main advocate. The Mooninites enjoy boasting that the Moon is superior to Earth in every way, often referring to Earth objects or concepts as "primitive," though they can never prove this superiority even when they attempt to do so. They spend most of their on-screen time harassing the Aqua Teens and Carl, engaging in theft and other illegal activities, and attempting to corrupt the innocent Meatwad with criminal tendencies and vices (including smoking, drinking alcohol, and "shooting the bird"). The Mooninites have only two apparent super powers: they can join together and fire the "Quad Laser," a large, red, extremely slow-moving (and easily dodgeable) square video-game bullet, and the "Quad Glacier," a larger, slower version of the Quad Laser.

The Plutonians, Oglethorpe and Emory, are two spiny extraterrestrial creatures who sport nothing but sweatbands. They aspire to eventually conquer the Earth, but instead spend more time devising bizarre, ill-advised ideas (such as using disco lights as force fields) and bickering with each other. They command a huge spaceship that they barely know how to fly.