Flying cars The flying car is one of the most common requests when people are talking about future technology. "We were promised a flying car; where is our flying car?" Although there do seem to be commercially available flying cars in the 30th century, that doesn't make them a good idea. To illustrate the impracticality of the flying car, imagine a typical rush hour at an intersection near you. Now, extend that snarl to a third dimension. Add hyperloop tubes, all manner of starships, and various flying aliens to the mix, and the flying car begins to seem more like a mobile coffin than a means of transportation.
Interstellar parcel delivery The cast of Futurama all work for Planet Express, a delivery business that specializes in transporting parcels throughout the known universe. From a physics standpoint, this entire business model is a scam. According to Einstein's Special Theory of Relativity, as an object approaches the speed of light, it also approaches infinite mass. In order to deliver anything over galactic distances in a reasonable length of time, a transport ship would have to exceed the speed of light, thereby increasing the mass of its cargo to infinity and beyond. If charging their client by weight, every package delivered would require infinite resources to ship. On the plus side, that infinite price tag is a flat rate that does not change with the volume of the merchandise.
Heads in jars One of the unique aspects of Matt Groening's vision of the future is the ubiquity of heads in jars. From important cultural symbols like Pauly Shore to popular political icons like Richard Nixon, it seems like every celebrity from history is still around, chatting with anyone that enters their field of vision. These heads never seem to have anything of value to add, and just crave attention. While it is nice to see that the heads of Adam West and Burt Ward are still getting work, is it a good trade-off for having to live beneath the tyranny of Richard Nixon's head?