傻瓜好歹是个瓜笨蛋好歹是个蛋
[shă guā hăo dăi shì gè guā bèn dàn hăo dăi shì gè dàn]
This nickname uses playful wordplay to describe someone as foolish or silly but also implies that there's a kind of honesty in their nature: being a 'cucumber' (瓜, gua) or an 'egg' (蛋, dan) in a metaphorical sense, accepting their imperfections.