Can and iPhone 4 or 3 case fit on an iPod 4th generation?

I have an iPod but not an iPhone. My friend said you can put an iPhone case over an iPhone. I course it's not gonna fit very well but does it at least work a little. Enough that I won't slip out all the time. Which iPhone case would go best with an iPod 4?

Iphones are much bigger than ipods it will slip out

None, I've tried that before, they are too deep and the wrong shape!
Sorry!

I've tried putting my iPod 4 into my Dad's iPhone case and my iPod was so thin that it fell out.