There are currently 4 dimensions available to explore in the Multiplayer version of Pocket Mortys. They are Mortyland (Dimension 1), Plumbubo Prime 51b (Dimensions 2), Mortopia (Dimension 3), and GF Mortanic (Dimension 4). Each dimension has different Mortys available to capture.
Updated to Game Version 2.25.1, Asset Version 278 (June 14th, 2021).
Disclaimer: As an Amazon Associate we earn from qualifying purchases.