The kids' reply was funnily cruel: treat or trick.

孩子们的回话厉害得不行：不请客，就捣蛋。

Treat or trick is their slogan, they can always get the candy.

不给糖就捣蛋是他们的口号，他们总是可以得到糖果。

Monday night is trick-or-treat time!

周一晚上是不给糖就捣蛋的时间！

If children play the game called Trick or Treat, what's the festival they are having?

如果孩子们玩的游戏叫“不给糖就捣蛋”，那他们过的是什么节日？

They knock on their neighbours' doors and shout "trick or treat".

他们敲了他们邻居家的门，然后喊着“不给糖就使坏”。