The great physicists and philosophers of our times have speculated on the existence of parallel universes. They have spent uncounted amounts of time and money studying this possibility. That is all unnecessary.
Dogs have long known about parallel universes. They just know. If you have more than one dog and a house with more than one door going to each available yard, your dog will demonstrate to you which universe is what. For demonstration purposes, let us say you have two doors to your front yard. Your dog will use whichever door goes to the universe he wishes to visit. The same with doors to the back yard. I have four pointers and often doggysit weimaraners and bassets. They all run to the doors when it is time to go outside. However, depending on the time of day and what they want to do out there, they will go to different doors. Note, all the doors lead to the same universe that I expect to be there, but they go to different universes that the dogs expect to be there. They never get lost, though, because the always come in the right door to get back to this universe.
I fully expect that these dogs are so ethical that they would never defecate into the wrong universe. I also see notices of lost dogs on the local power poles. I suspect that these dogs never got back to the right universe.