Why is the same joke funny when someone tells it, but not when others tell it?

This is mainly caused by the feelings of people who listen to your jokes. Although human beings have evolved well, they still can't get rid of the shadow of animals' perceptual knowledge of things. You may have told the same joke to different people in the same tone and posture, but you will have different reactions, which shows that the other person's personal perceptual knowledge will affect the perception of your rational ability.