At least that's what Jess thought. As Jess settled down atop the back of the couch, Mary did the unexpected - she dipped her snout under one end of the couch and with a mighty heave of her shoulders, flipped the couch over.
Jess was caught off guard, and had no time to prepare, no time to correct her trajectory, and hit the floor hard, with the couch coming down swiftly atop her. It hit with a loud, resounding cruch, and Jess yowled in pain. Her hind legs were not only broken, they were quite effectively crushed.
Jess was pinned under the couch, and the furious Mary just glowered at her, sympathy entirely absent from her dark, beady eyes.