When I was waiting for my operation I asked my colleagues to send me jokes to help me to stay cheerful. This was one of my favourites:
A girl asks her boyfriend to come over on Friday night to meet her parents and have dinner with them. Since this is such a big event, the girl tells her boyfriend that after dinner she would like to go out and make love with him for the first time. The boy is ecstatic, but he has never had sex before so he takes a trip to the pharmacist to get some condoms. He tells the pharmacist that it's his first time so the pharmacist spends some time talking to him and tells him everything there is to know about condoms and sex. At the cash register the pharmacist asks the boy how many condoms he'd like to buy - a 3-pack, a 10-pack or a family pack. The boy decides on the family pack because he thinks he will be rather busy, it being his first time and all.
That night the boy turns up at the girl's parents' house and meets his girlfriend at the door "Oh, I'm so excited for you to meet my parents, come on in!" She takes him into the dining room where her parents are seated at the table. The boy immediately offers to say grace and bows his head. A minute passes and the boy is still deep in prayer, with his head down. Ten minutes pass and still no movement from the boy. Finally after he has spent 20 minutes with his head down his girlfriend leans over and whispers to him "I had no idea you were this religious". The boy turns and whispers back "I had no idea your father was a pharmacist!".