Is this something that's illegal?

I made a fake facebook account that's a duplicate of my friend's account, I added all his friends and liked all the same things he liked. I did it as a prank so that he will be like wtf at the duplicate account, and I have a couple friends that are in on it, but I can't help feeling like I can get into some kind of trouble for this. Can I? I guess if I did it would count as Identity theft, but It's not an EXACT duplicate and I'm deleting it after I get his reaction though. So is it illegal?