He had a grin on his face like a Cheshire Cat.

他咧嘴一笑像只柴郡猫。

《柯林斯英汉双解大词典》

"I've often seen a cat without a grin," thought Alice; "but a grin without a cat!"

“我常常看到没有笑脸的猫，”爱丽丝想。“但却没见过只有笑脸没有身体的猫！”

youdao

Alice: that's what's not cat about you - that silly grin!

爱丽丝：那个愚蠢的笑容就是你不像猫的地方！

youdao

He is the Cheshire cat whose grin never fades, a brilliant televisual politician whose ready wit unerringly turns his opponents' strength against them.

ECONOMIST: Bagehot