All credit goes to the original "Gazmik/Datagutten" for this incredible addon.

Ported and fixed for Classic.

New in classic version:

Integration into the built-in "Addons" menu when pressing ESC.

You're able to enable/disable functions in here.

Fizzwidget's Hunter's Helper has been ported aswell.

Original description for the addon:

As my Hunter friends can readily attest, keeping a wild pet can be a full-time job. Why, just feeding the critter when he gets hungry can throw off your routine -- you've got to rummage around in your bags, find a piece of food, make sure it's appropriate for his diet, and check your aim before tossing it to him (lest you accidentally destroy a tasty morsel). So inconvenient! Not to mention potentially dangerous... you don't want to spend so long digging through your bags that you or your pet become someone else's snack.

Never fear, Gazmik Fizzwidget is here with a new gadget to automate all your pet-food-management tasks! My incredible Feed-O-Matic features state-of-the-art nutritional analyzers to make sure your pet's hunger is satisfied with a minimum of fuss, advanced selective logic to make your pet doesn't eat anything you have another use for, and a weight optimizer to make sure the food in your bags stays well organized! You can have it automatically feed your pet when needed -- or, if you're worried about running out of food while you take a nap, you can opt to manually press the "Feed Now" button and it'll intelligently choose a food and accurately toss it to your pet. This is actually one of the first gizmos I started work on... but because I'm a perfectionist I haven't considered it ready for release until now.

Features:

Makes feeding your pet quick, easy, and fun:

Bind a key to "Feed Pet", and Feed-O-Matic will automatically choose an appropriate food and give it to the pet whenever you press it.
Alternately, Feed-O-Matic creates a button next to the default UI's pet frame -- click this button to feed the pet.
Can use an emote to notify you when it's feeding your pet, with custom randomized messages. See FeedOMatic_Emotes.lua to customize them to your characters!

Helps you manage all the pet food in your inventory:

Keeps track of which foods your pet likes more, and prioritizes "better" foods when choosing what to feed the pet. Also makes sure not to use foods your pet has "outgrown" or foods not appropriate to your species of pet.

If you're on a quest to collect several of a certain item which also happens to be something your pet likes to eat, Feed-O-Matic can avoid consuming it. (Unless you're carrying more than is needed for the quest or there's nothing else for your pet to eat.)

Manages four major categories of foods: Conjured food (free if you befriend a mage), Basic food (just restores health; found at many vendors), "Well Fed" food (has bonus effects when you eat it; often comes from cooking), and Raw food (things that aren't edible for you, but are for your pet; often used as cooking ingredients). Feed-O-Matic looks for food in this order (Conjured, Basic, Well Fed, then Raw), to prioritize the food that's cheapest (both in terms of cost to you and potential usefulness). You can use the Feed-O-Matic Options panel to avoid feeding your pet entire categories of food, or to avoid just specific foods.

Feed-O-Matic keeps track of what foods are used by Cooking recipes. The Feed-O-Matic Options panel shows which foods are ingredients for which recipes, so you can choose to avoid feeding things to your pet that you'd rather cook for yourself.

All other things being equal, Feed-O-Matic will try to pick foods from smaller stacks, making sure your food supply doesn't take up all your bag space. When your bags get close to full, Feed-O-Matic will start ignoring other criteria and always choosing the smallest stack so that you won't run out of inventory sooner.

Fizzwidget Feed-O-Matic Classic