The writers have obviously kept the name of the MIB a secret for a reason. I believe the name will be a crucial plot element and will be identified in a mind-blowing reveal. Here is my theory on his name. Don't read further unless you want your mind reduced to atoms and accelerated through the Large Hadron Collider.
The name of the MIB is...
Vincent. That's right, the MIB is a time-travelling supernatural dog. This ties together two huge mysteries, the MIB and Walt's special powers. When did we realize Walt was special? After he got Vincent as a pet. Some of the MIB's powers must have been transferred when Walt was petting Vincent. Why did Walt appear soaking wet and speaking backwards? Because Vincent had just licked his face with…Read more >