Can I guess for a prize?
You're using the cargo hold backdrop, which has aliens, stars, and rocks inside a container.
Round 1 was the rock candies which match the astroid plushies
Round 2 was the star confetti matching the shooting star plush
you've alluded to round 3 being sentient, and that would line up with it being the only thing left in the cargo hold container:
mini aliens
It could be a triangular prism. You may never know what the staff have in sight.Is the jar cube-shaped?