The blowfish first appeared in Marine Mine. Highroller had allied with them and was leading them on a mission against Big Green, though his plan was discovered by Lady Green and Stingray King. Before they could make an escape, they were attacked by blowfish warriors, though they ultimately managed to return to Big Green to alert its forces. The blowfish then made an frontal assault on Big Green, wherein Blowfish King demonstrated his ability to puff to extreme size. At this size, he could singlehandedly damage large parts of Big Green base. He was only defeated when a pump was inserted into his mouth such that Sammo Whale could suck the air out of him and deflate him. The defeated Blowfish were then convinced to ally with Big Green.
Blowfish King later aided Big Green during the events of The Bronze Giant Part I / The Bronze Giant Part II. When Big Green base was converted into a massive mobile battle station, he was affixed to the tip of its "tail," like a massive spiked ball. He later joined the other 107 heroes in forming the Bronze Giant.
The blowfish are known for their ability to puff up to increase their size, and in this state, sharp spikes hang off their bodies. They can control these spikes individually. Blowfish King can attain a massive size, comparable to that of Big Green base, and can stab with great force. When the Bronze Giant used Blowfish King's powers, it displayed the ability to shoot spikes, likely indicating that Blowfish can do the same.
- In Marine Mine, it is shown that the blowfish inflate themselves with air, whereas real world blowfish inflate with water.
- The CGI promos depict numerous characters in the background, all but one of which are season one animal leaders. The exception is one that appears very strongly to be Blowfish King. This suggests that the blowfish were conceived while season one was still in production, but did not appear until season two.
- This is further supported by the appearance of Blowfish King in materials relating to Hero: 108 online, an MMO game loosely related to the first season of the cartoon.
- The inflated blowfish resemble underwater explosive mines, which seems to be referenced in their debut episode, Marine Mine. Oddly, aside from this, nothing in the episode has any apparent relation to mines, nor do the blowfish have any relation to them other than passing resemblance.