The Giant Fish Balloon Monster is a villain in The Powerpuff Girls. He appeared in the episode "Uh Oh Dynamo". When the evil giant fish balloon monster appears from under the water he tried to ruin all the people of Townsville's fun and games. The girls tried to stop him but he proved to be too strong, injuring them in the process. Soon he goes on a rampage by destroying Tokyo Townsville. The girls used the Dynamo to stop the evil giant fish balloon before he got defeated by pointy wheels shaped like ninja stars.
The fish balloon monster also appears in the music video for Signal in the Sky, a Powerpuff Girls themed song by The Apples in Stereo. His role in the music video is similar to his lone episode appearance. The fish balloon monster peeks out of the water and begins terrorizing the city of Townsville.
He steps on citizens, crushes cars, destroys a monorail bridge, body slams the city hall to smithereens, breathes fires in surrounding buildings and makes an attempt to attack the band who perform the song. He manages to get his fin through the window but can just barely touch a member of the band. It is right then and there the Powerpuff Girls come to save the day as the monster is chewing on a chunk of the building. The girls start punching and kicking him before one final knock down makes him collapse on the ground, defeated as police cars surround him.
The Fish Balloon Monster is a big, red, thorned monster who can expand and change his size when he chooses to. He apparently has a child, who follows in his father's footsteps and attempted to scare off people in Tokyo Townsville as well.
He is the most strongest monster the Powerpuff Girls have faced, and he cannot be fought without some kind of contrapment, being almost invincible. By holding his breath in, the monster can shoot his spikes out of his back like shrapnel. Given his place of origin, the fish balloon monster uses elements of Japanese culture as weapons such as using a monorail train as a pair of nunchucks. He can also breathe fire. Because of his expandable rubber body and pointy spikes, he may be based on a puffer fish; this also makes him vulnerable to sharp objects as well.