Petropolis 11 (ペトロポリス11) is an action-adventure video game developed by Burst Arts Inc. and Dimps and published by Namco. The game follows Thunder, Bolt, and Soul as they discover the motive behind the Z-Monsters' scheme of reviving Moe, the mischief king. Like with the previous game, players are to explore hub worlds, complete certain levels, and defeat many bosses. It was released on May 4th, 2007 in Japan and May 25th, 2007 overseas.
Three years have passed since the events of Petropolis 10, and peace began to settle on the Petro Islands. Bolt is beginning to learn more about his best friend's new morphman companions. Julie is doing more research on some of the morphmen Thunder found for her and learn that they can not only morph into different objects, but also into different forms. Bolt wonders if Thunder's morphmen can also undergo such a process. Julie attempts on making Yolk and Blur transform, but to no avail.
Later, the three and the others were invited by White Aether, a science group formed from the ashes of the Shadow Dragon Foundation, to their building. Soul, once seeing a message from one of their employees, believes he can find more answers from that organization, so he also joins his friends to visit the new facility. Little did they know that a mystical race of Z-Monsters is right behind them, planning to reawaken the mischief king of the Dark Ages.
- Thunder Storminski: Remains the same from Petropolis 10, but later gains a new morphman, Rage.
- Charles Drafters: A pegasus beastman who was one of the three who agreed to the Hybrid Project. He and his two partners were saved by the Garage Kids during Hybrid's tournament, thus shutting the bio-fighter down. After a reunion with Thunder, whom he, Sal, and Idris knew since childhood, he agreed to join the Garage Kids and save the islands. Charles is the wielder of the Glacier Gauntlets, allowing him to control ice.
- Sal Greenspike: A stegosaurus beastman who was used as one of the three components for the Hybrid Project. He and the other two have recovered since then and are ready to join the other Garage Kids, as well as his friend Thunder, in their duties. Sal's Sacred Weapon, the Eco Brooch, allows him to control plants and natural life.
- Idris Lionheart: A lion beastman who, along with Charles and Sal, was originally a part of the Hybrid Project years ago. Since the other Garage Kids saved him, he decides to reunite with his closest friend Thunder and fight evil together. Idris wields the Flame Armor, which he wears to control and radiate fire.
- Bolt Cinnastar: Has his abilities from Petropolis 10, but now has Glide and later an astral being named Serenity.
- Milton Redder: Has his shapeshifting abilities from Petropolis 2, marking his first appearance since aforementioned game.
- Gerald: The reformed G-65 can also morph certain parts of his body into weapons.
- Angus Ward: Bolt's partner from Petropolis Pocket returns to assist. He is briefly playable before being injured by the attacks of the vicious Z-Monsters.
- Soul Squareshell: His abilities from Petropolis 9 have been nerfed to suit the style of the game. At some point he becomes possessed by Z-Monster mage Tile and attempts to kill the beastmen.
- Mix: A wolf morphman from the Ancient Isles. Dubbed by some of the morphmen as their guardian, he watches over them to make sure no monstrosities threaten them. Eventually he finds Soul's possessed body and used a morphman named Pine to try and heal him. It was revealed that Mix met Thunder prior to the game, referring him as his "master" due to his loyal behavior towards him.
- Tile: A miniature Z-Monster who arrived from a desolate island unknown to the beastmen. He and the other Z-Monsters plan on reviving the mischief king Moe by slaying many beastmen, believing that "the blood of those with life shall awaken that who creates disorder." His wish may have been fulfilled, but he was killed by Moe.
- Karex: A dinosaur-like Z-Monster who is Tile's right-hand man. He had a part in slaying those who try to prevent the Z-Monsters' goal of awakening Moe. While on the Petro Islands, he froze Loren and their partners and invited Thunder, Bolt, and Soul to Tile's mansion to fight his other minions. Karex was defeated by Bolt while they were on the final room of the mansion.
- Moe: A yellow-furred monster who is known as the "mischief king." Despite his jolly appearance, he is regarded as dangerous due to the fact that he turns anyone into crayon drawings. When Soul's violence accidentally awakens the beast, he sets off to transform everyone into drawings for his "collection" and will tear anyone who is "drawn bad."
- Super Chimera Thunder (Thunder+Yolk)
- Mega Chimera Thunder (Thunder+Yolk+Blur)
- Hyper Chimera Thunder (Thunder+Yolk+Blur)
- Super Dragon Soul (Soul+Daisy)
- Z-Monster Soul (Soul+Tile's magic)
- Mach Bolt (Bolt+Glide)
- Celestial Bolt: The fusion of Bolt and the passing Serenity. When she was about to die, she pleaded Bolt to use her magic to defeat Moe. Celestial Bolt can fire magical bullets in addition to stronger "lightning quakes."
- Thundersoul (Shocksoul in Japanese): The fusion of Thunder, Soul, and their morphmen. It was through the act of the morphman fusing together and saving their respective owners from Mega Moe. Thundersoul is capable of performing "electric-ice attacks."
- G-Red: The fusion of Milton and Gerald with the use of White Aether's Gattai Gloves. He resembling a life-sized robot with the features of his components. His mechanical body can also morph into weapons.
- Jolly Moe (normal form)
- Mega Moe: Moe's 2nd form after getting absorbed by his "evil" drawing, a muscular and menacing version of Moe.
- Powerd Moe: Moe after absorbing the drawings of G-Red and Bolt (and Serenity, to an extent). With this form, he attempted to recreate everything to appeal to his chaotic nature. Thunder and Soul were able to escape to the Ancient Isles thanks to their morphmen, but they had to find a way to restore their world to normal. After the original Moe was separated from his corrupted self, Thunder and Soul fuse and finish the job, reverting the world back to normal.