Hogatha's magic locket is a locket that Hogatha owned in the cartoon show episode "Bewitched, Bothered, And Be-Smurfed". She says that it is the source of her power, inherited from her grandmother Dogatha. As she flew off into the dark stormy night with her pet vulture Harold, however, a lightning bolt struck the bird, sending them plummeting into the forest where Hogatha lost her locket. Realizing that her locket was gone, she sought help from the evil wizard Gargamel who reluctantly agreed to help her find it.
Smurfette found her locket and decided to keep it when she called out to whoever lost it and got no response. As she wore it, though, the magic locket granted things that Smurfette wished for, though not in the way she intended them to be fulfilled and mostly without her being aware that the locket was granting her wishes. First, Greedy's house was full of flowers. Secondly, Greedy was turned into a walking fiddle when Smurfette wished that he was up and about and "fit as a fiddle". Thirdly, Jokey became a literal philosophical giant when Smurfette wished he'd "grow up and get serious". And fourthly, Grouchy's attitude became overly cheery.
After a while of the Smurfs witnessing these strange transformations, Smurfette began to realize that it must have been the locket she was wearing and decides to drop it back into the forest with the hope that good luck would return. However, she ended up dropping it into Gargamel's possession when Hogatha ended up abandoning him in order to reach the Smurfs by transforming herself into a frog and claiming to be a beautiful princess in need of a kiss from a handsome Smurf. With the locket in his possession, Gargamel wished for all the Smurfs to be on a silver platter, and instantly he got his wish.
Hogatha, who as a frog was left alone in the village when that wish was fulfilled, sought after Gargamel and found him back in his castle with her locket. Although Gargamel had thrown Hogatha out, she came back in to provide a distraction so that the Smurfs could escape from being in the locked box. As Gargamel chased after the escaping Smurfs, he slipped on a ball of string and fell, causing the magic locket to fall off him. Hogatha grabbed it and used it to change back to her original form, then grabbed Smurfette with the intention of using her as her servant girl. Smurfette then grabbed Hogatha's locket and threw it to Papa Smurf, who then threw it into the fire in Gargamel's stove, destroying it so that nobody could use its power anymore. As it was destroyed, the transformed Smurfs were changed back to normal, and Hogatha disappeared in a green mist, saying that when the locket is destroyed, so is she.