IPhones, can I trick people?

Okay, so I got the iPhone 4 recently.
But I would of preferred the iPhone 4S. Don't get me wrong, I'm completely contempt with the 4 and I love it.
But I kinda want to trick people into thinking I have a 4s, not a 4.
So I was just going to get a big bulky otter box, and just pretend its a iPhone 4S.
Will this work? As long as I keep the case on and don't let someone look at my phone for too long?
Last time I checked the iphone4 and 4s look almost exactly the same.

What if they ask you can you use siris