"Grim or Gregory?" is a Halloween episode of the animated TV series The Grim Adventures of Billy and Mandy. It first aired in the United States on the Cartoon Network on July 26, 2002.
It is Halloween and Billy, Mandy and Grim go trick-or-treating. While Billy and Mandy are at a house, Grim mistakes a boy's mother for Atrocia, the host of the all-night Halloween Marathon on TV. Gregory is mistaken for Grim by Billy, and Grim is mistaken for Gregory by Gregory's mother. By the end of the episode, everything is back to normal.