How to set a different value in the generator meta tag?

Actually there is no hook there to change the texts on the fly. So the way is like below:

Let’s first remove the default one, use the following code in functions.php:

remove_action( 'wp_head', 'wp_generator' );

Now show our new one, add the following code in functions.php:

function wpse_custom_generator_meta_tag() { 
   echo '<meta name="generator" content="Mr. Kauwa Kala" />' . "\n";
}
add_action( 'wp_head', 'wpse_custom_generator_meta_tag' );