Here are some randomly selected joke topics
Spaceman
What do you call a crazy spaceman?
An astronut.
The Titanic
What do you get when you cross the Atlantic with the Titanic?
About half way.
Giraffes
What do you get if you cross a giraffe and a dog?
An animal that likes to chase low flying aeroplanes.
The Sea
Jill: You remind me of the sea.
Jack: Because I'm wild, unpredictable and romantic?
Jill: No, because you make me sick.
A Born Loser
A born loser: Somebody who calls the telephone number that's scrawled in lipstick on the phone booth wall -- and his wife answers.
Doctors
Doctor, Doctor I keep thinking I'm God.
When did this start?
Well first I created the sun, then the earth...
Snakes
What do you get if you cross a snake and a lego set?
A boa constructor.
Revenge
How do you get your revenge on a doctor?
Give him a taste of his own medicine.
School
Teacher: Today I want you to write an essay on an elephant.
Pupil: But won't we fall off?