After defeating Necrozma, Phyco and Soliera in Ultra Moon or Dulse and Zossie in Ultra Sun will arrive with a Poipole in tow, telling them that it is interested in joining them. The player can accept or refuse; in the latter case, they can always return to Ultra Megalopolis to pick it up again.
A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.
In the manga
Megalo Tower in Pokémon Adventures
In the Pokémon Adventures manga
Megalo Tower first appeared in the Sun, Moon, Ultra Sun & Ultra Moon chapter. It serves as the headquarters for the Ultra Recon Squad while also providing artificial light for the Ultra Megalopolis. After a Stakataka appeared at the Ultra Megalopolis looking to fight with Necrozma, Zossie took Sun and Moon to the Megalo Tower to hide, as they had no way of fighting it. Stakataka grabbed Sun, forcing Moon and Lunala to fight it to rescue him. While they battled, Soliera appeared, revealing that she deliberately lured Stakataka to them so she could see how the bonds between a Trainer and their Pokémon could lead to a way of restoring light to the Ultra Megalopolis.