Phone Codes

11-yr-old girl.  A week or two before this, I'd left the room quickly for something.  When I returned, she had my phone in her hands, with the screen asking for a code. 

Girl: What's your code?
Me: I'm not going to tell you that.
Girl tries a combination.
Me: You're not going to work it out.  Give me the phone, please.
Girl: No, I can get this!  I just want to... [incorrect, again] Oh.  ... Um, change something cool in your phone...
Enough incorrect attempts that the phone locks.

Part 2:
Girl:  Ooh, can I borrow your phone for something?
Me: Er, no.
Girl: Pleeeeeease???
Me: No.
Girl manages to grab phone from me.
Me: You don't know my code, so that's a bit pointless.
Girl [indignant]: Yes I do.
Me: No, you don't.
Girl: Yes, I do.
Me [starting to laugh, she is so adamant]: Really?  What is it, then?
Girl [wide-eyed, serious]: Well, I can't tell you - I don't know if this is the real you, and not someone pretending to be you.

All I could do was laugh.