Dzień dobry tosterze - Good morning to you, toaster!

The vocative case is one that should be really straight forward.  Of all the grammatical cases, it is the one that seems to have the clearest rule.  It is used when you are addressing someone.

For example: 

Mamo, gdzie są moje skarpetki? - Mum, where are my socks?

Mama is being addressed so takes the vocative form Mamo.

So the next time I talk to my friend, I use her name in the vocative case.  Oh no, no.  You don't do that these days in speech.  Just use the nominative case for people's names, unless it's Mum or Dad etc.

OK got it.  Used rarely in speech, but used in writing.

But, why do everyday objects have a vocative form?

Should I be talking to my toaster?

When the vocative form was assigned to all nouns back in antiquity, did they predict that one day in the future there would be chirpy talking toasters offering grilled baked goods and light banter?