Bonkers appears to be a gorilla-like creature who wields a large hammer and has no true eyes. He also seems to be wearing pants and a "jacket" with slits in it for his arms. The muscles on his arms are concentrated to the area around his supinator, in a similar fashion to Popeye.
Bonkers lived in a jungle until a circus crew captured and trained him for the circus. While Bonkers was held against his will, the ringmaster decided to watch his favorite show, which was the Kirby show. This is how Bonkers got inspired to meet Kirby in person, so, without letting the circus find out, he quietly escaped and wandered off to Dream Land in search of his favorite hero.
When he finally got to Dream Land, the Cappies at first thought he came to battle Kirby, but soon everyone learned that Bonkers really wanted to train with Kirby. Knowing this, King Dedede had plans for Bonkers, so first he asked Bonkers to impress Kirby with his hammer skills, and tried to smash Kirby with a boulder, but Bonkers smashed the boulder with his hammer to make sure his favorite superhero wasn't hurt at all. Dedede finally resorts to taking him all the way to his castle and getting Nightmare Enterprises to turn Bonkers into a monster. He was later returned to normal, however, and he left, hoping to continue his training.