As someone who has been on here a decade, I have never thought to ask. Is there a way to mass feed my pets? I've acquired a lot of them and feeding them one item at a time is tiring.

You can put them in the resort or Inn. This will keep them fed and happy. If you do Drills quests make sure to leave one out for manual feeding and playing with. Also if you're doing the gourmand achievements, then keep that pet out as well.

Another, more expensive. way is to buy an Infinity Berry.