1. What in the world was that?

in the world：究竟，到底

例：
Why in the world are you doing such a thing?
你们到底为什么做这种事情？

What is the most important thing in the world?
这个世界上到底什么最重要？

2. A pixie!

pixie：小精灵

例：
Standing behind the counter was a pixie of a woman manning three phones at once.
一位像小精灵一样的女人站在柜台后面，同时应付着三个电话。

3. To neverland.

neverland：梦幻岛

例：
Neverland is not never found. It is where you were there.
梦幻岛不是没有办法到达，它即是你存在之地。

I made his Neverland dreams come true.
我让他的梦幻庄园梦想变成现实。

4. Of course, I couldn't go without Michael and John.

go without：没有...也行

例：
We can go without food or water for a few days.
没有了食物和水，我们能活几天。

In fact, this practice should go without saying.
实际上，这个常识不用我说。