twit 笨蛋，傻瓜，讨厌鬼
He is a real twit.
他就是个笨蛋！

knucklehead 笨蛋
Do you know anything about these knuckleheads that got caught allegedly stealing?
你知道那些因为涉嫌偷东西被抓的笨蛋吗？

airhead 笨蛋；傻瓜
She's a total airhead!
她完全是个大傻瓜！

squarehead 笨蛋；无能的人

clown 蠢货，笨蛋
What do those clowns think they are doing?
那些蠢货自以为他们在干什么呢？