For anyone who has been writing code for any length of time, you’ve no doubt encountered the the occasional error of “TypeError: null is not an object”. The cause is obvious once you understand what different types can be defined. But the first time you encounter it without any awareness of what types are, it can be absolutely maddening to grok and correct.
Because I have a strange sense of humor, I renamed my iPad, iPhone, and notebook… with even less meaningful variations of the TypeError:

It seems the Apple TV doesn’t accept some variant of that naming type. Could be the inclusion of the colon, or spaces, or even the length of the name. Too lazy to track down the reason.
Also, don’t forget that the name you assign in the Sharing pane of System Settings is also applied to the system HOSTNAME var. The first time after a week that I’d opened one of my terminals, I found myself wondering, “Why is the .bashrc throwing an ‘NullTypeobjectis…’ — oh, duh…”
Hmm… I wonder if they’ll tolerate unicode characters.