What jokes do you know that can make people laugh?

I'm from the south and went to college in the northeast. Half of my dormitory is from the northeast. In winter, my roommate solemnly said to us, "When you first came to the Northeast, you didn't know that the iron railings in the Northeast were all sweet!" This sentence has been unanimously recognized by roommates in Northeast China. As a result, a roommate in the south really believed it and licked the iron railing ... and his tongue was frozen.