This week I'm catsitting for a friend of mine. I'm not staying over or anything, just going over twice a day to feed the cats and clean the litter box. There are only three rooms in her house that cats are allowed in.
1. The kitchen, which you enter upon opening the back door.
2. The bathroom off the kitchen that contains the litter box.
3. The sun room off the kitchen.
The other door to the kitchen is a swinging door, so to prevent the cats from getting to the rest of the house, she blocked the door on the other side so it can't be pushed open.
Yesterday, one of the cats was somehow in the room on the other side of the swinging door. It took a lot of carefully clutching the edge of the door to PULL the door open so I could bring the cat back in to the kitchen. I checked the blocking thing and reinforced it.
Today I went over and both cats were in the forbidden zone. Ninja cats is the only explanation.