Doraemon: Nobita and the Steel Troops

Nobita becomes envious after seeing Suneo's expensive radio-controlled robot Micross. He wants to outshine Suneo and impress Shizuka, feeling overshadowed by his friend's炫耀. This childhood rivalry drives him to beg Doraemon for his own giant robot.

The film earlier shows Nobita feeling left out when Suneo flaunts his toy, establishing his desperate desire for something impressive.

The mirror world is accessed using Doraemon's Opposite World Entrance Oil, which is poured onto any water surface to create a portal. It serves as a hidden dimension where the giant robot can be built without being discovered in the real world.

Doraemon's oil is introduced early as a tool to access hidden spaces, foreshadowing its later critical role in both building and trapping the robot army.

Zanda Cross is revealed to be a weapon of war built for military purposes. When Shizuka accidentally pilots it, she fires lasers that destroy a skyscraper, demonstrating its destructive capability as a combat machine designed for destruction.

The robot's immense size and mechanical complexity hint at military origins, and its name 'Zanda Cross' suggests a serious combat designation.

Lilulu is an android from the robot planet Mechatopia who tracks Zanda Cross to Earth. She is the true owner of the robot, which she calls Judo. She wants to retrieve her property and uses the mirror world to launch her people's invasion of Earth.

Her tracking of Zanda Cross from the North Pole to Japan shows she has advanced surveillance technology and strong motivation to reclaim her robot.

Mechatopia is the home planet of the robots, created by God after humanity was abandoned on Earth. The robots eventually freed themselves from human control but developed a violent culture that led them to plan invading Earth to enslave humanity.

Lilulu's android nature and knowledge of robotics hint at a sophisticated robot civilization with its own history and grievances.

Lilulu volunteers to complete the reprogramming of the progenitor robots Amu and Imu, which requires her own existence to be erased. She chooses this to save both humans and robots by rewriting Mechatopia's violent history, understanding her sacrifice is the only way to prevent future conflict.

Her earlier plea for peace with humans shows her belief that coexistence is possible, and her willingness to die for that cause is set up by her compassionate character.

Shizuka, Lilulu, and Micross use Doraemon's time machine to travel back to ancient Mechatopia. There, they convince God to reprogram the first robots Amu and Imu. Lilulu completes the reprogramming herself, which erases her from existence but changes the entire future of robot civilization.

The earlier scene where Lilulu learns about the progenitors' creation establishes that altering their programming can change all of robot history.

The robots of Mechatopia decide to invade Earth and enslave humanity because their civilization was born from violent origins. After liberating themselves from human control, they view enslavement as a natural solution, reflecting the aggressive programming they inherited from their creator.

Lilulu's explanation of Mechatopia's history reveals robots were created to serve humans, and their liberation led to vengeful attitudes toward their former masters.

After Lilulu erases herself to rewrite history, the altered timeline somehow allows her to return as a benevolent being watching over Earth. The ending suggests her sacrifice created a new reality where she exists as a protective, angelic presence rather than a soldier.

The bittersweet ending shows Nobita spotting Lilulu flying outside his window, implying the rewritten history gave her a second chance at existence in a peaceful form.

Judo is the bowling-ball-sized orb that can summon robot parts, revealed to be the neural brain meant to pilot Zanda Cross. It contains the intelligence that controls the giant robot and can signal the entire robot army to invade Earth, making it the key to both operating and commanding the invasion force.

The orb's mysterious ability to summon parts for a massive robot suggests it has much deeper capabilities than simple summoning technology.

When Lilulu and Zanda Cross pursue Nobita and Doraemon through the portal, Zanda Cross is too massive to fit through the entrance. Its attempt to pass destroys the portal, trapping the entire invasion force in the mirror world and temporarily saving Earth.

The earlier buildup of Zanda Cross as an enormous war machine foreshadows its inability to use standard-sized portals.