A wobble base provides a curved floor-contacting surface with one or more alignment posts that align the wobble base to the bottom of a seating platform and one or more holes separate from the alignment posts through which one or more fasteners may be placed to attach the wobble base to the seating platform, thereby providing a wobble stool. The wobble base can be configured to convert an existing stool into a wobble stool by replacing one or more floor-contacting members with the wobble base. In a second embodiment, a seating platform, such as a stool, is provided with both traditional floor-contacting members, such as feet or casters, and with a wobble base that allows the traditional floor-contacting members to be removed and replaced with the wobble base, and allows the wobble base to be removed and replaced with the traditional floor-contacting members.