The plant

It is a small seedling tree that was growing in a broken fridge on Earth. It was discovered by WALL•E after he split the fridges door in two with his head-mounted laser. Despite it being a plant, it plays a very large role in the film.

When WALL•E sees the plant, he digs it up and puts it in an old boot he had found earlier. WALL•E takes the plant to the WALL•E transport vehicle where he lives and where he takes all the interesting items he finds.