Whether you think the joke falls flat or not is a matter of taste.

The joke fell flat, even in his own mind.

But the joke fell somewhat flat for the human beings.

But the joke fell flatter than my hair under a head scarf.

This is not because the jokes fall flat, though some have found them to.

This may explain why many jokes in films just fall flat.

The joke fell flat when he made the mistake of trying to explain it.

She stared at them, apparently realizing how flat her joke was falling.

Every now and then, however, the joke falls flat.

The one joke I did tell, which everyone at home would laugh at, fell flat.