X-PO is one of the non-playable characters in LEGO Dimensions and a returning character in LEGO Dimensions 2: The Rise of Enoch who also acts as the in-game guide.
In the opening sequence to LEGO Dimensions, X-PO and Lord Vortech arrive in Foundation Prime. X-PO goes scanning for something, and finds the Foundation Element pedestals. Lord Vortech says out loud his scheme to use the Foundation Elements to warp all of space and time. X-PO tries to explain to Vortech that if he were to do that, all of the universe could be destroyed. Unamused with X-PO's exposition, Lord Vortech disassembles X-PO and sends him to Vorton.
Later in the game, Batman, Gandalf, and Wyldstyle see a few pieces fall off of the Vorton portal. These pieces form X-PO, who will from then on in the game give the player hints on how to deal with certain objects.