老的就卖萌小的就装老
[lăo de jiù mài méng xiăo de jiù zhuāng lăo]
"Old ones acting cute, young ones pretending to be old" refers to a playful and ironic way of describing people who act contrary to their age, where elders pretend to be younger and cuter, and the young ones behave more mature. It implies role reversal in personality traits across different generations.