User blog comment:IamJakuhoRaikoben/Chapter 422: Orochi's Fin, Review./@comment-180.191.64.5-20150302155917

You're all giving up on Happy way too soon... Maybe he didn't feel like showing off his combat skills and magic that he has developed in training. Perhaps he thought that the enemies were too much of a fodder bunch to go in combat mode.

This is Happy we're talking about... This cat believes that the two most important things in the world are CARLA AND FISH (when they were getting "absorbed" by the demon whose name I forgot in the Tartarus Arc)... Perhaps developing the self-control in eating fish at every given moment is harder for him to do than to develop his magic and skills.

This cat has spent his entire life hanging out with a nutcase like Natsu... so it's possible that he has also grown up to be a fellow with strange priorities in life...

I wouldn't be surprised if he suddenly springs up some awesome magic:
 * four-winged Happy... very large wings
 * scale-skin or razor-fin or tigershark Happy for marine missions or when hunting fish
 * sustained sonic-boom flight
 * a human form that he would rather not show because he prefers his cat form and only shows it when he is forced in a physical confrontation or when catching fish
 * armoured wing Happy
 * farsight or infrared sight or just plain immensely heightened senses to locate the enemy or fish when he's hungry... HE'S A CAT AFTER ALL... so he is a natural predator no matter how cute he is... and also because, among him and Lily and Carla, he's the one closest to his "inner cat"... cats are usually playful especially with their prey before they eat it...

Have faith in Happy.