"oh here's something, now start doing all kinds of different things to it, but they MUST be different".
That's not how you play the box game really. You start out by clicking any interaction, whether it's a repeated one or not, so the dog knows that doing anything with the box is acceptable. This can (and should) include something as small as looking at the box to begin with. Once your dog is attacking the box sort of like Rocky was in that video, performing all kinds of different things, you need to put away the box for a moment to think.
Decide a specific action you want to teach your dog. Ideas could be: "push the box down the hall with your nose", "pick the box up and hold it", "flip the box on end with your paw", "stand with both feet in the box". Now you start shaping your chosen behaviour.
Slice the behaviour up into many smaller pieces. I'll use two feet in the box as an example. The first click would be for moving a foot towards the box. Once the dog is offering that behaviour, increase the criteria. Only click and reward for moving the foot closer and closer to the box. Once the dog is close to the box, up the criteria again. Now only click for a foot inside the box. Next for standing still with one foot inside for 1 second. Next for two feet touching the box. etc etc etc until you have the final behaviour of standing with two feet in the box giving eye contact. At that point you can name the behaviour "stand in your box!" or something like that.
The real creativity of the dog is not in seeing how many random things it can come up with, but in letting the dog "solve" the problem you have put forward with no input from you other than rewarding successive approximations.
Once he starts, say, touching the box and I click him for it, and then he does it again and I don't click - he's going to wonder why not and get confused/frustrated because he doesn't know what to do - other than to push the box harder.
He's already playing the game perfectly. What you're supposed to do is up the criteria once he gets frustrated and tries harder. You originally treated for touching the box. Now you withheld that treat so he's pushing the box. Now you treat only for pushing the box 3 inches. Once he's doing that, you withhold the treat. Now you only treat for 6 inches. All of the sudden you have a command where the dog can push a box 10 feet down the hallway for you!
