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