IDIOMS

Grin like a Cheshire cat

(Also smile like Cheshire cat.) To smile very broadly. This is an allusion to a fictional cat popularised by Lewis Carroll's depiction of it in Alice's Adventures in Wonderland and known for its distinctive mischievous grin.

Example: He knew that she was fearing a scandal. He stood in front of her, grinning like a Cheshire cat, waiting for more money in return for his silence.