Johnny was rather prone to being injured.
He got bit by a snake.
He got the monkey virus.
He got hit by a car.
He slipped on a climb and hurt his ribs.
He got hurt in an explosin in the episode, "Surprise."
He got his leg slightly burned in one episode and treated himself at ER.
He hurt his shoulder and was told he was soft by Dr. "No Bedside Manner" Morton.
can't recall any others at the moment.