What is the difference between 傻瓜 and 笨蛋?
Literally 笨蛋 and 傻瓜 mean stupid and silly respectively. I would say, as a native speaker,  笨蛋 is used as a negative adjective for others while 傻瓜 is more teasing especially for the the speakers themselves. Also, it depends on the status of the speaker and listener, for example, we will call the kids 笨蛋, but call the wife 傻瓜 when they make the same mistake.