Colonial animals are the edge case here. Most would be hesitant to say an ant colony is "an animal", but are happy to refer to a Portuguese Man 'o' War as such, despite also being a colony.
Man o Wars are also not disjoint. They have specialized cells, but I believe share nutrition among the non-feeding cells. A truly disjoint creature would need a metabolic system on both sides of the disjoint, a separate nervous system, and perhaps most difficult, a way to pass messages across the disjoint quickly enough to be useful (aka electric impulse).
At a certain point, I think it starts becoming dubious whether it's a single creature. Even if they're genetically identical, they start to look more like twins than a colonial creature.