What is similies words of

A clown is as funny as a

A similes for that is A clown is as funny as my sister falling

or a clown is a funny as a dog barking you really have no wrong answer with that

Similes compare two things. Because clowns are considered by most to be very funny, the object would also have to be something funny.

Therefore you could say ...

A clown is as funny as a medieval joker.

A clown is as funny as a cat barking like a dog.

A clown is as funny as a comedy movie.