This page explains how to recruit Mojo in Chrono Cross: The Radical Dreamers Edition.
Mojo is a living straw doll (don’t ask) chilling in a basement in Arni Village in Another World.
How to Recruit
Before triggering the event at Opassa Beach that sends you to Another World for the first time, you must obtain the Shark Tooth by speaking to the fisherman in the basement of the upper-right house in Arni Village.
After arriving in Another World, during the window between defeating Karsh and company at Cape Howl and before sneaking into Viper Manor at night, visit the same fisherman who gave you the Shark Tooth in Another World’s Arni Village.
You’ll discover he’s a Mojo-worshipper in this world. Open the Key Items menu and show him the Shark Tooth. Afterwards, attempt to leave the basement. Mojo–the straw doll–will come to life and join your party.