Originally just 'a dog catching a frisbee' (
盘 'plate / disc'). It became internet slang aimed at Hu Xijin, longtime editor of the Global Times (
环球时报 Huánqiú Shíbào), nicknamed
叼盘侠 'frisbee-fetching hero' for loyally relaying Party messaging. Now used for anyone seen parroting state-media talking points.