Superman's powers have developed, and his adventures have accumulated, far beyond the Fleischer cartoon's intonation of a character "faster than a speeding bullet, more powerful than a locomotive, and able to leap tall buildings in a single bound." Initially the character could not fly, but this ability and many more have added to the character's appeal. Superman's weakness to kryptonite, now well established, was introduced quite late in the character's history, first appearing in the radio series in 1943. Superman's large cast of supporting characters includes Lois Lane, Jimmy Olsen, and Perry White, while many adventures have seen the character pitted against villains such as Lex Luthor, Brainiac, and Doomsday.