As with the fantastic posters we showed you before, these helpful warnings are the work of Amy Kate Martin, whose Flickr stream includes bumper stickers for two dueling brands of clones. ("The You You Always Wanted" is one slogan.) This time around, the posters are warning against loose robots, careless changes to the time stream, and burning the whole prehistoric world down. The 826 Los Angeles store sells time travel goodies, and also teaches literacy and writing skills, since temponauts may actually need to be able to read the instructions on their time-capsules. Just maybe.