Needle-through-arm is a magic effect that was popularized by comedy actor/magician Harry Anderson. The trick can either be performed as part of a stage magic or a parlor magic routine. As the name would suggest, needle-through-arm relies on shock value to be a comedic effect.
In presentation, the magician produces a hat pin, roughly ten inches long and demonstrates that it is sharp by using it to pop a balloon. He then proceeds to sterilize the underside of his forearm with alcohol and, holding his arm so that it is not facing the audience, insert the needle through the skin of his arm. From the audience's perspective, this is not very impressive until the magician lowers his arm for the audience to see. The needle appears to pass about two inches under the skin. The new wound then appears to bleed, with the blood dripping down the magician's arm. The needle can be slid back and forth through the wound. After the needle is removed, the magician cleans his arm which can be offered for inspection.