Fuel efficiency is a big deal for car buyers today, even with gas prices currently delightfully low. To use less fuel, we have smaller engines, more turbocharging, hybrids, and so on. Sure, it all can save a driver money, but, you know, a car that was made to just steal its fuel would really solve things. And a company actually tried that: Dunkley, in 1901.
Now, Dunkley never came out and said their car was designed to steal gas, but let's look at how it was designed and the big selling points of the car. In 1901, the small Dunkley company from Birmingham, formerly known for making baby prams, went into production with their "Patent Self-Charging Gas Motor Cars." Since this is the UK, and they use the wrong words for everything, "gas" here isn't referring to gasoline, which they adorably call "petrol," but rather coal gas, or natural gas, which was commonly used at the time for street and interior lighting.
The big selling point of these coal-gas powered cars was that there was on-board equipment so the car could refill its gas tanks from any old gas pipe or, even more conveniently, any streetlamp.
So, think about what that means, and how great it is: you're driving around the city, and notice that your giant brass gas-level meterometer's needle is indicating that you're on "Nearly Depleted; Please Refuel Post-Haste, Kind Sir." So, you pull over and park by the side of the road, next to one of the innumerable street lamps. You whip out your little hose, plug in, fill the tanks, and then maybe stop for a wad of boiled mutton or whatever the hell they snacked on back then.
So... who paid for that fuel? Not you, clever Dunkley driver! Thanks for the fill-up, Uncle London Gas-Works! Or, should I say, Uncle Sucker Gas-Sucker!
The Dunkley Self-Charging Gas Motor Cars were built for four or five years, but never really caught on. At least, I don't think they did, since I can't find any record of legal action from the Gas-Works lobbies or anything like that.
After Dunkley was finished with their parasitic coal-gas cars, around 1923 they returned a bit to their roots and started making some really crazy stuff: motorized baby prams. They had this little one-wheel-and-motor unit that would connect to the back of one of their prams, and a nanny could stand on that while driving the baby carriage all around town.
It was easily as safe as shoving a baby carriage around with half a scooter. These started with little 1 HP, one-cylinder two-strokes, but you could later get a 750cc 21 HP motor for your baby carriage, just in case you wanted to give your child the gift of a really exciting death.
Plus, being motorized, most of these prams had to be used on main roads with normal, full-sized vehicle traffic and not in parks and places like that. Oh, and indoor use is probably not recommended, since 2-stroke exhaust was probably understood to be bad for babies, even in those dark ages of medicinal cocaine.
Cars designed to steal their fuel, and a 21 HP baby carriage? Dunkley, you're a freaking kook.