恍然

Tony glanced at her, then did a double take .

托尼瞥了她眼，过才然大悟。

The speaker gave us a humorous joke which suddenly clicked with us and we all laughed.

"演说的人给大家讲了个话,使下子然大悟,于是都哈哈大起来。"

I wasn't used to such good treatment, then it clicked : we were wearing suits.

不习惯这么有礼的招待，随然大悟：是因为穿着西装。