How to animate a ball inside a jar using physics and collision

So, I created some high quality artwork. I think you can do what you are after! Kinda. As long as the head moves slowly (the balls came out of the head otherwise, which could be funny I guess).

If the blue top is in the same layer as the green, the red dot gets pushed out as I suspected. But if the blue top is independent, marked with collide as well, then the ball gets trapped inside! Because there are no dangles etc on the blue layer, it just stays in place.

But if you move the jar too quickly, then the ball can jump through the sides of the container. Oops!

What Collide and Dynamic tags have you added to the ball and head? (I think the ball needs both and the jar needs collide.) I am not sure if it will cope with a closed container however - you might try first with an open ended container (a "U" shape) and see if that works, then if it stops working when its closed... ummm... time for plan B! But start with plan A and see how far you can get.

Plan B starts experimenting with shared puppets. I have never done this, but wondering if you can trick it by superimposing a second character over the top of the real character, so it does all the physics with an open top. I suspect a closed object is just too hard for CH to understand. I think it just works out the contour of the shape. I guess you could try tricks like independent jar lid, to see if it ignores independence with collisions etc. Its all about getting a continuous shape that is not a hole i think.