WALL-E (Waste Allocation Load Lifter: Earth class) (voiced by Ben Burtt) is a little robot who is the main character in WALL-E.
Because WALL•E has been alone for 700 years, he has developed a "glitch": sentience and a personality. He has become very curious and he keeps anything interesting he can find. Even though he still obediently follows his directive, WALL•E can get distracted, collecting the trash rather than compacting it. His most prized possession, "Hello, Dolly!", teaches him how to hold hands, which he considers the way to say "I love you."
He has become very lonely, having nobody but Hal as company, and is beginning to wonder whether there is more to life than his directive. So when he meets EVE, he quickly falls in love with her. WALL•E is very protective of EVE. When she shuts down after getting the plant, WALL•E places her on top of his transport (thinking she is charged by solar energy just as he is) and protects her from the weather waiting for her to "recharge". At the repair center, he mistakes that the equipment there as trying to hurt her and rushes to her aid.
WALL•E's friendly demeanor has an effect on the other robots and humans he meets. For instance, he causes M-O to act on his own, leaving his pre-set travel path to follow WALL•E trying to clean him, and he teaches TYP-E how to wave good-bye. He also breaks John and Mary out of the technology-induced reverie that consumed the lives of all the other passengers aboard the Axiom, wherein they learn how to enjoy the world and each other's company for the first time in their lives. Even the dirt on his chassis provided Captain B. McCrea the impetus necessary to become interested in the history of and subsequent return to Earth. Most importantly, he is instrumental in EVE's growth and development, from rigidly following her programming to learning how to love him in return.
WALL•E was designed to be an environmentally-friendly garbage-processing robot. As such, he possesses many interesting devices to help him fulfill his directive.
Construction: He has twin, extending, hydraulic arm shovels with articulated fingers mounted on U-shaped tracks to his sides. His locomotion is achieved with treads sporting four independently-actuated sprockets for stability. The tracks on his treads can be removed by unclipping the hinge pins on a single joint. His front opens up his body cavity in which he gathers and compresses trash. His head contains his audio-visual sensors mounted on a long, articulated neck, enabling him to see in any direction. All his extremities - arms, treads, and head - retract back into his cube-shaped body for easier storage, referred to as "boxing" in the movie script. He reverts to this shape whenever sleeping (or hiding). A hook on his back served some unknown purpose (perhaps for self-storage aboard the transport). He now uses it to carry around his Igloo cooler full of interesting bits of trash he picks up. His hull is reinforced, mostly to give him the strength necessary to compact trash in his body cavity. As such, he is able to survive most environmental dangers, including long falls, extreme heat, the vacuum of space, and being trapped in a hydraulic actuator much larger than himself.
Regeneration Unit: He has a solar-powered regeneration unit as his power source. Super-high-efficiency solar panels unfold from the top of his chest and recharge the batteries contained adjacent to his control system. These batteries are capable of powering him for upwards of a day's hard work. A read-out on his chest gives his current charge level, and beeps an alarm when his power level has drained dangerously low. The panels can be removed to expose auxiliary battery leads that can be used to jump-start WALL•E, or for him to jump-start some other electric mechanism.
Control System: All of WALL•E's control electronics are contained within the cavity in the front of his chest. All of his systems are controlled through a central motherboard. WALL•E's eyes are camera lenses, indicating that visual recognition is his primary means of navigation. They can magnify and resolve images at a distance, even independently if necessary. In addition to visual, he appears to have audio and some rudimentary tactile sense, given that he can detect things that his hands or treads touch. He also contains an alert system, warning him when dust storms are approaching on Earth's surface. Speakers mounted to his chest allow him to communicate audibly. He possesses a recorder with external controls - stop, record, play - which he uses to record songs from the Hello, Dolly!. What function it originally served is unknown (perhaps to play and record Buy n' Large jingles and slogans to humans before they left Earth).
Trash Disposal: Two powerful hydraulic presses on his back operate his compactor function, compressing trash in his body cavity into neat cubes that can be easily stacked and carted away. His strong, dexterous arms enable him to create stacks of trash blocks hundreds of feet high with incredible precision. Between his eyes is a high-power laser, which he typically uses to cut large pieces of trash into manageable pieces. He has a fine degree of control over the device, as he is able to use it to carefully engrave his and Eve's names on a metal trash can.