(Man visits doctor about a sexual problem..)

Man: Doctor I feel terribly embarrassed, but I've got a 'small' problem...when I make love with my wife, I have a 'small' problem..you know......I'm a bit small...

Doctor: Hmmmm, now when your in the bar with your friends, what do you drink?

Man: I drink Fosters!

Doctor: Aha! Now there's your problem you see..when you drink Fosters it makes things shrink and go smaller! So what you need to do is to drink Guiness instead!

Man: Guiness? You mean that black Irish bitter stuff?

Doctor: Yes! Guiness is good for you! It makes you big and strong! If you need to get bigger, drink Guiness!

Man: Thankyou doctor! I will try that!

Doctor: Good! I'll contact you in a months time to see how you are getting on!

(One month passes..)

Doctor: So how are you getting on now?

Man: Oh fantastic! My sex life is just great now!

Doctor: Good, so your drinking Guiness now?

Man: Are you kidding? I've got my wife drinking Fosters..

Doctor: