Poo is the prince of Dalaam, a faraway kingdom built at a great height. He is beloved by his people, appearing to be especially popular with the women. Before his meeting with Ness and his friends, Poo is seen undergoing the Mu Training under the guidance of his mentor, the Star Master. When he finishes his training, he learns Teleport, and uses this newly-learnt technique to teleport away to Summers, where the three other main characters are waiting for him.
Later, after exiting the Scaraba pyramid, the Star Master takes Poo away temporarily to teach him PSI Starstorm α. Later, in Deep Darkness, Poo re-appears in the battle against Master Barf, and lands the finishing blow with this new technique. Near the end of the game, the Star Master returns once again to teach Poo PSI Starstorm Ω in the Cave of the Past, so he can go back in time and defeat Giygas.
Poo appears as a trophy in Melee.
Poo appears as a sticker in Brawl.
Poo makes several cameos in Magicant when the background rips to reveal several points in Ness' adventures.