I was/I were conundrum - please explain

[scattercushion]

The children's book: I Wish I was You
Should it be I Wish I were You?

Because we say: 'If I were you' don't we?
Or am I wrong? Please advise, oh learned ones.

I think it whould be I wish i was you because you wouldn't say I were.... about anywhing else.

You're right scattercushion.

We say "I wish I were you" because this is the subjunctive mood that has largely been forgotten in English but lives on in some fixed expressions like this.

Other examples: "God save the Queen" "If I were you..."

It should be 'I wish I were you' because of the subjunctive that Cies mentions, but 'I wish I was you' is now considered grammatically correct too.

Cies, are you in TEFL? I seem to remember you live in Galicia?

You're right. The subjunctive mood follows wishful statements. It's similar to this thread in pedants' corner...
www.mumsnet.com/Talk/pedants_corner/654376-If-I-were-a-boy-Beyonce