Hero Plants are some new plants in Journey To The West. They have different abilities and special skills, and they can be moved by the player at any time. You can only use one Hero Plant in each level, and once it is eaten, you cannot re-plant it again for the rest of the battle.
Electric Anemone, Vigorous Broccoli, Pomegranate Machine Gun, Carrot Missile Truck, Oak Archer, and Ghost Pepper have the upgrade plant seed packet, even though they are not upgrades. This was mostly intentional to prevent the plants listed above from getting imitated by Imitater.
They are all unlocked by purchasing them at the shop.
This isn't the first Journey to The West inspired game created by Popcap. In Bookworm Adventures Vol. 2, the 5th Book: The Monkey King, has characters inspired by the novel.