Here are some randomly selected joke topics
Cows
Knock, knock.
Who's there?
Tilly.
Tilly who?
Tilly cows come home.
Waiters
How did you find your steak, sir?
I just turned over a chip and there it was.
Scottish
What is very smelly, and is spoken in the highlands of Scotland?
Garlic.
Frogs
What do you get if you cross a palm tree with a frog?
A croakanut.
The Ocean
Why is a Christmas pudding just like the ocean?
it's full of currants!
A Comedian
Patient: Doctor, I keep thinking that I'm a comedian.
Doctor: You must be joking.
Lunch
Knock, knock.
Who's there?
Justin.
Justin who?
Justin time for lunch.
Owl
Knock, knock.
Who's there?
Owl.
Owl who?
Owl aboard!
Computers
Profanity is the one language all programmers know best.