After somebody finishes telling a joke, say in a very grave tone,
"My brother (sister/mother/father) died that way."

On the bus, try to engage somebody in a conversation about genital warts.

Call a house at random, and ask for Gary. When they tell you that
there's no Gary there, call again a little while later. Do this at
intervals about four times. Finally, when they're fuming and about
to scream bloody murder, call a fifth time, and say, "Hi, this is
Gary. Are there any messages for me?"

Exclaim in a crowded theater, "No, I won't touch you there for a
dollar! No, not two dollars, either!"

When someone asks, "Are there any questions?" ask, "Where do
babies come from?"

Take an envelope, fill it with baking powder or flour, and send it
to somebody.

Follow a few paces behind someone, spraying everything they touch
with a can of Lysol.

Zombie Punk, you are funny. While sitting at a red light, right when it changes green begin honking your horn at the person directly in front of you.

who says it has to be green?

the laws of the road dont apply on the road

Every time someone begins to speak to you, hand them a breath mint.