Here are some randomly selected joke topics beginning with the letter 'C'
Cafeteria
Bacteria: The rear portion of the cafeteria!
Cafeteria
Did you hear about the idiot who thought that bacteria was the rear of a cafeteria?
Cabbage
What is green and goes 'boing, boing, boing'?
A spring cabbage.
Cage
How did you get here? Did someone leave the door of your cage open?
Cab drivers
Did you hear about the idiot who thought a taxidermist was someone who stuffs dead cab drivers?
Cake
He's a few currents short of a fruit cake.
Caddy
"How should I have played that last shot?" the bad golfer asked his caddy.
"Under an assumed name."
Cake
What did the cookie say to the unhappy cake?
"Hey, what's eating you?"