In my basement is a recreational room with what appears to be a pool table, but I'm using it to house a couple small pet crabs, maybe two inches across.

The crabs are being attacked by some sort of mechanical bird. I see one of these birds land on the pool table and stab its beak at a crab over and over again, each time missing the crab and striking the table surface. The crab gets under the bird and grabs at it with its claws, but the underside of the bird is a metal cylinder, so the crab claws have no effect.

Then a bird attacks a crab on the floor, which is not where the crabs are supposed to be. The crab skitters quickly over to the edge and disappears through a hole in the wall, into a dirt-floored basement space adjacent to the room.

I take some stairs into the basement area and start looking for crabs. They are all buried in the dirt, but as soon as I walk around down there, they feel my footsteps and start digging out, popping out of the dirt and waving their claw aggressively at me. These crabs are much larger, 6 or 8 inches across. I keep moving to stay away from them; they seem more interested in defense than giving chase. But everywhere I step, another crab crawls out.

My friend Mark happens to come down the stairs, and I warn him to be careful about all these crabs that are now infesting the place. I'm going to have to do something to remove them all.

(note: I did happen to be looking at little crabs at the pet store a couple days ago)