By editing the file Launcher_profiles.json (C:\USERNAME\AppData\Roaming\.minecraft) a user is able to change the name of which they are called in the game, simply go down to the bottom of the file and edit the user name, the image (attached) shows this, this is similar to the old launcher prior to minecraft 6.1, so far this doesnt work on servers seeing as you need to log in to play, but off line and on LAN games you can call your self whatever you want. this isnt major, but you may want to fix it some how. I lined out the things under pink cause of privacy issues if you need them you should be able to get my email by my username
Cheers, Zac