Well @Larry by combining two objects and then adding a third object in them,You can combine three objects,Below is a more precise example
For example- Imagine a plastic toy duck and then add a key in it(The one found in mechanical toy duck with a steel key which rotates when you move it) and then combine it with another object by changing its shape slightly either by removing a line or by slightly altering the shape of each object slightly to get an object which contains 3 objects),
Note-This was not my idea I had posted some of my ideas to an text generation ai by a website and I this idea along with many other ideas as a result,
Cheers.