Answer: Star Trek’s Hypospray
In the Star Trek universe, the Hypospray is a needleless medical device designed to transfer liquid medicine and other substances into the patient without the use of a traditional needle-based injection. At first blush, it seems perfectly natural to have such a device on Star Trek; such devices have long been considered a future invention waiting to happen and their appearance isn’t limited to the Star Trek universe.
And yet, the inclusion of the Hypospray wasn’t driven by the desire of Star Trek writers to be cutting edge in all technological matters. In early scripts, the doctors and attendants on the show used regular old 19th century-era hypodermic syringes to inject medication. It was brought to the attention of the writers, however, that the use of hypodermic syringes on the show was strictly forbidden by NBC’s broadcast standards and practices guidelines. While such a restriction seems absurd to the modern viewer (who lives in a time of wildly popular medical dramas that feature not only syringes, but all manner of blood and mocked-up medical emergencies), the broadcast standards for television networks in the 1950s and 1960s were far more conservative, and the presence of syringes and injections, even in a legitimate medical situation, were considered too inappropriate for public consumption.
As a result, writers created the Hypospray, a tool that allows for medical injections without a visible needle since the tool used a burst of focused pressure to push the medication through the skin. Although never formally confirmed, it was long rumored that the prop used in the original series was a repurposed and slightly modified automotive fuel injector. If so, that would be slightly ironic given that one of the first recorded incidents of a person being injected with something via the mechanism the Hypospray works on was in 1937, when a worker was injected with diesel fuel from the fuel injector of the engine he was working on.