HB: Do you have a girlfriend?
You: Yeah I've got 69 girlfriends. I send them a wagon of red roses and heart chocolate every single day.
->Really any random answer would do which is obvious to be a joke. The 69 is just the flavor
HB: How old are you?
You: Let's just say you're definately too young/old for me.
->Notice you're disqualifying her by saying that SHE's not appropriate age for YOU and not vice versa. Another option is:
HB: How old are you?
You: I'll celebrate my 5th birthday next june.
->She can laugh or...
HB: You're not 5 years old/You looked older/You're a liar/basicly any shit.
You: Oh haven't I told you? I count my birthday from losing my virginity.
->THIS IS RISKY. But is field tested. And if you can back it up with a shiny honest smile it will do magic
HB: What's your phone number?
You: I don't have a phone. A giant grizzly flew through my window and swallowed it yesterday.
->Again. Any random thing which would make her laugh but you're not giving out your number.