A cartridge comprising: a photosensitive drum; a casing having a first end portion and a second end portion opposite from the first end portion in an axial direction of the photosensitive drum, the casing rotatably supporting the photosensitive drum; and a coupling operatively connected to the photosensitive drum so as to be capable of transmitting a driving force toward the photosensitive drum, wherein the coupling includes: a main body, a movable portion movable relative to the main body of the coupling between a first position and a second position, wherein the movable portion is closer to the second end portion of the casing in the axial direction of the photosensitive drum when the movable portion is in the second position than when the movable portion is in the first position, and a projection configured to move away from an axis of the coupling relative to the main body of the coupling in response to movement of the movable portion from the first position to the second position, characterized in that when the movable portion is in the first position, the movable portion is positioned more remote from the axis of the coupling than the projection, and wherein when the movable portion is in the first position, the movable portion is positioned closer to the second end portion of the casing in the axial direction of the photosensitive drum than the projection. a photosensitive drum; a casing having a first end portion and a second end portion opposite from the first end portion in an axial direction of the photosensitive drum, the casing rotatably supporting the photosensitive drum; and a coupling operatively connected to the photosensitive drum so as to be capable of transmitting a driving force toward the photosensitive drum, wherein the coupling includes: a main body, a movable portion movable relative to the main body of the coupling between a first position and a second position, wherein the movable portion is closer to the second end portion of the casing in the axial direction of the photosensitive drum when the movable portion is in the second position than when the movable portion is in the first position, and a projection configured to move away from an axis of the coupling relative to the main body of the coupling in response to movement of the movable portion from the first position to the second position, characterized in that when the movable portion is in the first position, the movable portion is positioned more remote from the axis of the coupling than the projection, and wherein when the movable portion is in the first position, the movable portion is positioned closer to the second end portion of the casing in the axial direction of the photosensitive drum than the projection. a main body, a movable portion movable relative to the main body of the coupling between a first position and a second position, wherein the movable portion is closer to the second end portion of the casing in the axial direction of the photosensitive drum when the movable portion is in the second position than when the movable portion is in the first position, and a projection configured to move away from an axis of the coupling relative to the main body of the coupling in response to movement of the movable portion from the first position to the second position, characterized in that when the movable portion is in the first position, the movable portion is positioned more remote from the axis of the coupling than the projection, and wherein when the movable portion is in the first position, the movable portion is positioned closer to the second end portion of the casing in the axial direction of the photosensitive drum than the projection.