Pet = Cursed Sapling seems to have the best effect in the game from a pet!
Light Pet = Wisp from aWisp in a Bottle
But I so what this Light Pet "Suspicious Looking Tentacle" if it is added or whenever it gets added from Moon Lord's Treasure Bag in Expert Mode but I haven't even fought Moon Lord on normal yet.
And minions are something entirely different they are from staffs that attack like Slime, Imp, Raven, UFO, Pygmy and many others and I have Slime, Imp, Raven, Pygmy and UFO I like UFO and Raven.