坐过红沙发 (zuò guò hóng shā fā) - A "geng" is a joke/punchline. A "black geng" is mockery of someone (usually celebrities), which is negative. "Playing black geng" means bringing up someone's embarrassing memes in an entertaining way. (People often claim they mean no harm) Example: Cai Xukun is often memed with his basketball playing and "Chicken You're Too Beautiful" (misheard lyrics).