Poo's Master's sprite from EarthBound.
Poo's Master is a character in EarthBound. He has Poo train to help Ness on his journey, sending him to meditate at Mu, the place of nothingness. After Poo has met with the Star Master and completed his Mu training, Poo's Master gives him a few levels worth of experience, allowing him to learn Teleport α and β before he leaves to join Ness and company. After this point, Poo's Master remains at the palace in Dalaam and will heal Ness's party for free at any time.
Poo's Master has no given name in EarthBound, but in the Japanese version of Mother 2 he has a specific name. "Yee-soo-chii" is a Japanese version of a Chinese phrase "Yi-Si-Qi"; this means "one-four-seven" and is a reference to a gameplay concept in mahjong.