I have seen my tokay play dead. I hold him on almost a daily basis (with gloves of course, trying to tame him) and two times I have placed him back into his tank, and he just lies there on his side motionless. I freaked out the first time, so i poked him and he bit me and ran up the glass. The second time i knew what to do and poked him, and he just ran away. He hasn't done it for a long time. I think it might be a defense mechanism in certain geckos. My cresteds and leos have never done it. Hope this helps to ease your mind.