I brought with me, but did not use, adhesive shelf liner (sometimes called "contact paper"). The plan was to put this sticky-side-up on Art's work surface, so that when he stepped over the cube wall he would find himself entangled. I had been a little reluctant to do this, since the goal was to confound him, not make him slip and fall (or stick and fall) when climbing in. By the time I got done with everything else, I was tired and didn't feel like doing this, so I skipped it. (My first thought was to put strips of duct tape sticky-side-up, but the shelf liner would have been easier to deal with. I'm not sure how well the adhesive would've performed.)
There was enough room to fit several more cardboard boxes. Unfortunately, the large boxes that Art had placed in my cube (including at least four 19" monitor boxes) had long since gone to cardboard recycling heaven. I might have been able to find more of the smaller boxes elsewhere though. I also could have used something else to fill the cube (e.g. plastic peanuts), but because this was a response to a cardboard-based incident, a cardboard-based response seemed most appropriate.
I figured Art would come in the way he did. We could have made it much harder for him to enter that way. As it was, we didn't spend too much effort on making the northwest panel bulletproof, and we didn't spend any effort on locking down the southeast panel.
I thought about putting in a Nerf rocket-launching toy, and aiming it where I figured Art would be standing. The launch stand connects to a tube, which leads to a heavy rubber cushion. Stomping on the cushion forces air through the tube and launches the foam rocket. I could have run the tube under the cube wall to the east and disguised it, pulling it out and stomping on it right after the northwest top was removed. This seemed complicated, error prone, and I didn't feel like going toy shopping, so I skipped it.
Art has a catepillar toy that, when stretched, plays music. It's *really* annoying. I meant to stretch it to full length across his keyboard, binding it with twine, so that he would be forced to endure the music before he could use the keyboard again. This one I just plain forgot to do.
Art's arrival could have been better managed. I sent him an e-mail taunt at about 9:45am, which would have been better timing since a later arrival would have meant more people in the office (we're a late-arriving, late-working bunch). I wasn't really sure when he was going to be arriving, though I had talked to his manager on the previous Friday to be sure that he wasn't going to be out of town.
I thought about weaving a spider web of twine in the corners of the cube to impede progress, or perhaps a vertical one dividing the cube in half. It was difficult to push the twine through the holes in the cube walls though, so this would have taken a very long time to do. Might be doable by running the twine through small metal hooks, and then attaching those to the walls.