Happy Birthday: Bouncing Boy
Charles Foster "Chuck" Taine was an ordinary 30th-Century Earth boy who got a job running errands for a famous scientist. The scientist sent Chuck off one day to deliver his experimental super-plastic formula to the Science Council, but Chuck got distracted by a robot gladiator tournament and stopped to watch for a bit.
During the tournament, Chuck got thirsty and, in his excitement, he mistook the formula for a harmless soda and drank it! The drink transformed Chuck, inflating him like a ball and giving him the power to bounce like one as well. When doctors told him his super-bouncing ability was permanent, Chuck gave up his old job and joined the Legion of Super-Heroes as Bouncing Boy.
He later married his teammate Duo Damsel and retired from active service, though he remained in the Legion reserves.