The disease, a form of leprosy that affected animals, was thought to be incurable. However, a scientist named Dr. Silas Stone (the father of Cyborg) experimented with a serum that was designed to cure the illness. Unfortunately, the serum had an unexpected side effect, causing Garfield to transform into various animals.
This transformation ability, coupled with his agility and enhanced strength, became Beast Boy's primary superpower. The ability to shapeshift not only gave him a unique fighting style but also made him a valuable teammate with his adaptability and versatility.