Keychains are novelty LEGO items that are based on many different themes, including licensed themes. They are just like minifigures, but with a keychain on top. If one has the right equipment, they can make one with a duplictae minifigure. Each keychain commonly features minifigures, miniaturized sets, or single 4x2 brick attached to them. The link to the chain is usually attached to the top of the minifigure's head. Unlike the average LEGO bricks, most keychain related item are unable to break apart due to special glue-based affixing methods, but various ways to remove them have been demonstrated. Some methods, but various demage the initial keychains design permanently. They are part of LEGO's promotional products and follow a different numbering system than standard sets. This system has changed over time. SOme newer keychains include a molds for minifigures parts, in which the legs are attached to the head. Sometimes, the same keychain will be sold under different name.