忍俊不禁

tā de gù shi shǐ wǒ men rěn jùn bù jīn

他的故事使我们忍俊不禁。

He had us in stitches with his stories.

huí dá tā men de wèn tí shí zhēn jiào wǒ rěn jùn bù jīn

回答他们的问题时，真叫我忍俊不禁。

It was hard to keep a straight face while I answered their questions.