One example could be "as quiet as a cat".
Another example is "as crazy as a bag full of wet cats".
Some more are:
- A smile like a Cheshire cat.
- A grin like a Cheshire cat.
- As busy as a cat on a hot tin roof.
- As cautious as a cat.
- As agile as a cat.
- Complacent like a cat.
- As stealthy as a cat.
- Suspicious as a cat.
- Trippy like a cat on catnip.
Further Information:I recommend a book called Similes Dictionary by Elyse Sommer. You can find it in these places:
I also recommend a useful website called Simile Stack, though it may not be as insightful as the book. Click here to visit it.