Nitrous Oxide - Dr. Horace Wells

There used to be a time when Nitrous Oxide was a party toy as it makes people laugh and howl like hyenas. It's a laughing gas. But a friend of Well's took too much of it and gashed his legs during a staged show, and hadn't realized he'd hurt himself. As a result, Nitrous Oxide became an early form of anaesthesia.

Brandy - A Dutch Shipmaster

The Dutch Shipmaster used heat to concentrate wine in order to make it easier to transport. The concentrate is supposed to be reconstituted by adding water upon arrival. As a result, Brandy (Burnt Wine), which tasted better than the watered-down wine, is accidentally invented and became a big hit in Dutch.

Penicillin - Alexander Fleming

Halfway through an experiment with bacteria, Alexander went on a vacation, accidentally leaving the dirty petri dish in the lab sink. By the time he got back, he found bacteria had grown all over the plate, except in an area where mould had formed. That discovery led to Penicillin - a group of antibiotics derived from Penicillium fungi, effective against many serious diseases.