Part of me wants to make a giant spectacle of the thing. Show up with a ton of gear that you have to set down (directly in their way) while you you deal with the boxes. But I know that type of person would just complain even louder.

It sounds like you're in a different dept with a different manager. Assuming that your manager agrees, your manager should be the one to say no. That way, everyone on your team can simply say their manager won't allow it.

If that fails, the Wally Reflector is a good tactic. Tell them that you'd love to help, but they need to do something first. You can say that you're very busy, but you'll take the boxes if they flatten all of them and put them on a cart. It's still offering to help, but it requires work on their part. It also quickly reveals if the requester is just being lazy.

If that fails, treat it as a training opportunity- they must need training on a required part of their job, which is why they called you. Drag them along the whole time, explaining every detail to them. Bonus points if you explain the history of why we do it that way. Basically, make it more work for them to be lazy.