I am not seeing you registering the widget in this code.
For inside of a theme:
register_widget('WP_Widget_Mood');
For inside of a plugin:
add_action( 'widgets_init', create_function('', 'return register_widget("WP_Widget_Mood");') );
I am not seeing you registering the widget in this code.
For inside of a theme:
register_widget('WP_Widget_Mood');
For inside of a plugin:
add_action( 'widgets_init', create_function('', 'return register_widget("WP_Widget_Mood");') );