I have found more things about Dipper's real name. If you take a look at the picture above posted from IG account gravityfallstruefacts, it says that Dipper's real name is close to Mabel's name. Could this prove that his name starts with M? But it does open up another theory, could his name be Lebam???? In the episode The Deep End, when Mabel gets all the letters in bottles, there is one addressed to a Lebam. Could Mermando know that that is Dipper's real name and addressed a letter to him?