Photo: Diane Edwardson, October 4, 2012. The other morning, a neighbor awoke to find her cat playing with a large, leafy alien species. (Click on photos to enlarge.)
After killing it with a kleenex box, she realized she'd never seen anything like it outside of horror movies. The wings look like leaves, with finer, transparent wings beneath. The legs (including the spikes on the rear legs) and the head look grasshopper-like, but it has a small body.
Since you can search by shape of bug on www.BugGuide.net, and further refine the search adding "leaf like wings," I think this is a California Angle-Winged Katydid.
Photo: Diane Edwardson, October 4, 2012. Katydid and a size 10+ foot for scale.