Dragon Ball Episode 128: Secret of the Woods
Episode 128 of 153 of Dragon Ball, aired September 28, 1988, 25 minutes. Available with English subtitles and dub where released.
Episode summary
Continuing his training, Goku follows Popo's instruction and enters the deep, dark woods. While searching for a worthy sparring partner, Goku stumbles across a surprising discovery hidden deep within the secluded labyrinth and finds help a most unexpected way!