Technically yes, but the way the characters are rigged/animated makes it so completely replacing the geometry of the character is very hard. Texture changes and adding additional geometry seem to work fine, but I think something about the rig bones makes it so that you can't really character swap without some dark magic. A few modders have demonstrated some progress with this, but no finished projects yet. (For example, the dude who runs their modding package couldn't finish his own character.)
What toy are you using? And are you connecting via phone app or PC app, and LAN or dongle?