Users real name isn't showing up in mw.user.options.
It shows up in the preference page just fine, but for some reason it's not being propagated out to the javascript stuff.
I got around it by using the MakeGlobalVariablesScript hook, but that seems a less than optional solution for something that's should be a normal user preference.
Tested on MW 1.25.2 and 1.27.1
realname is not a regular user preference – it's really more like the email, which also isn't in mw.user.options. (Internally, it's stored in the user.user_real_name table column, rather than in the user_properties table.)
It would probably be easier (and maybe more sensible? I'm not sure…) to expose it in a similar way to the username (mw.config.get('wgUserName')).