pop into one's head
突然产生念头
A:Mike promised to help us.
A:迈克答应帮我们了。
B:Mike? How can you trust him to help us?
B：迈克?你怎能相信他的话呢?
A:Why not?
A：为什么不能呢?
B:He's too unpredictable. He says anything that pops into his head. And them he forgets it all.
B:他太让人难以琢磨了，他总是想起什么载说什么，过后就忘得一干二净。