Well at first both of the cats liked to get on top of the playfield and try and catch the balls mid-game. Finally got them to stop doing that so much, and now one of them sometimes gets onto her back legs and tries to bat at my hands while I play, and finally the cats developed a knack for hearing when a coin door was about to be opened. So much so that I have to shut the door to the arcade when I'm going to work on a game. Well, today I was preoccupied and forgot to shut the arcade door. I opened a coin door for a second to get the key to open up the backbox, unlocked backbox, replaced key, shut coin door... long story short, 20 minutes later I heard meowing and couldn't find the cat--- yep, shut inside the machine.
Both cats have had to be fished out of machines a couple of times before we realized that this was going to be an ongoing problem not solved by spray bottles (after they are pulled out of course). Apparently I'm a slow learner with this one. Luckily no damage has been done yet, and I think I have finally had the "close arcade door when working on machines" lesson drilled into my brain.
The main culprit also thinks she's a topper.