These knock knock jokes are on one of the other blogs that I follow, so I can't take credit for them, but some of them are soooo funny if you have just been through 3 and 1/2 years of infertility treatments(which I have) and you are still quite bitter about your inability to become pregnant (which I am). Oh, by the way, these are posted on The Naked Ovary(link to the left)

Knock knock
Who’s there?
Pregnant
Pregnant who?
Everyone but you.

Knock knock
Who’s there?
Urine ass.
Urine ass who?
Did you think you were pregnant? Urine ass.

Knock Knock
Who’s there?
Your husband. And I don’t know why I have to knock. Where’s the other key?
My husband who?
See? Exactly! I knew it! All I am to you is a cup of sperm.

HA HA HA!