Someone is stealing my WiFi.

[slodave]

You need to change the name of your Macbook. When you connected to the other network earlier, that network assigned a different hostname - because of all the duplicates. Your Mac kept that name and when you plugged back in at home, the Mac gave it's current hostname - Michelle. After the reboot, hostname went back to MacbookPro and the random number.

A little more info:
https://discussions.apple.com/thread/1662243?threadID=1662243

No one is stealing your Wifi.

[porsche4life]

The hostname is now showing as the macbook 883 thing.... What I want to know, is how it came up with Michelle?

[slodave]

I just told you.

[porsche4life]

Originally Posted by slodave

No one is stealing your Wifi.

I realize that now....

[porsche4life]

Yes, I get that it was random... But why Michelle? Why

[slodave]

Would you have preferred Mandy?

Your Mac was assigned a name from the other network because of duplicate names.

[slodave]

Even more..
Local hostname involuntarily changed - MacRumors Forums

[Steve Carlton]

I am Michelle. Nice iTunes collection. Thanks!

[GH85Carrera]

Originally Posted by Steve Carlton

I am Michelle. Nice iTunes collection. Thanks!