In some states, prisoners are not allowed to bring small claims lawsuits. Other states have special procedures for prisoners who want to sue in small claims court. In California, for example, a prisoner who wants to sue in small claims court must file papers by mail and then either submit testimony in the form of written declarations or have another person appear on his or her behalf in court (Cal. Civ. Proc. Code § 116.540(f)).
In some states, military personnel who have been transferred out of state are also allowed to bring small claims court cases without having to appear in court personally. Check your state rules for information on how to do this.