Astro Boy (2004)

Astro and Dr. O'Shay take a visit down to Deep City, designed by Professor Sebastian. It's an underground city where anything and everything goes on, along with nature. Hannah, the tour guide, show Astro, Dr. O'Shay, and Sebastian the sights in Deep City, accompanied by Mayor Manny. However, the only thing Sebastian wants to see is the purification system. Manny takes him to where the system is, but Sebastian soon finds out that it's entirely fake. Sebastian is outraged by this, immediately confronting Manny about this hoax. Manny doesn't see what the big deal about it all is, but Sebastian explains that the purification system lets the trees, plants and everything else to continue growing. Without the system, all will die and oxygen will no longer be created. Manny blows him off. Sebastian goes to drastic measures to ensure that this won't happen. He creates a formula to make the plants grow indefinitely, but the whole thing gets out of control. The plants and trees grow at no end, with the roots harming people and taking over the city. Astro tries to contain them, but fails. Manny says to Sebastian and the rest that the cost was too high to build the city, leaving nothing left for the system to be installed. Astro continues, attempting to destroy the roots, but it's no use. They just keep growing. Astro sees that the only tree that won't grow is the oldest and tallest tree in Deep City. He suggests that he could maybe talk to the tree to see if it knows how to stop all this. O'Shay jumps in saying that the tree's bioelectricity could interact with Astro, if done properly. The machines set up next to the tree, and Astro finds out what's causing the plants to grow so much. It's the sap. Now that they know what's causing it, Sebastian must create an antidote. Meanwhile, different kinds of robots are let loose to destroy the never-ending plants. Astro tries preventing the robots from doing anymore damage, telling them that it's not the trees fault. Sebastian has success making an antidote. O'Shay gives it to Astro and gives him instructions to spread it all over the city. Astro succeeds and all the plants go back to normal. Mayor Manny is arrested. O'Shay informs Sebastian that since he made the plants grow so much, he'd be arrested too, but O'Shay would be at his case testifying that he also made the antidote.