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Folk who have this have Fast User Switching enabled — the menu bar name allows you to switch between users... er... fast
 
  1. System Preferences
  2. System
  3. Users and Groups
  4. Login Options
  5. If everything is grayed out, click the lock in the bottom left corner and enter your password
  6. Show Fast User switching menu as "Full Name"

EDIT: Jaffa Cake is tasty, delicious, and...fast. (Much like the user switching.)
 
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