Among the many different versions of The Flash across the DC Universe, their origins are all pretty similar. Usually, a speedster gains their powers after a lab accident, usually involving a lightning strike or something similar in nature. The original Flash, Jay Garrick, gained his powers in a lab accident, but it occurred under some of the dumbest circumstances in all of comics.
Jay Garrick was the very first hero to become The Flash, first appearing in Flash Comics #1 (1940) by Gardner Fox and Harry Lampert. When Barry Allen was first introduced in 1956, Garrick was turned into a literal comic book character for the new speedster, as he was seemingly wiped from existence in the DC Universe. Famously, Garrick would return in Flash #123, as he became The Flash from Earth-Two. His return was the first time the multiverse was truly brought to the forefront in the comics. Over time, he would become a key member of the Justice Society of America and has been a reoccurring character on The Flash television series, played by actor John Wesley Shipp.
In Jay Garrick's first comic appearance, the story wastes little time into jumping into the speedster's origin. Garrick was a student at Midwestern University, who is first seen getting rejected on a date with a classmate because she sees wasted potential in him, as "a man of your build and brains could be a star..." and he's just a "scrub." Garrick is next shown in a research lab, as he's studying special gasses from "hard water." As the experiments go deep into the night, Garrick decides he needs to take a smoke break. However, after taking a puff, he accidentally knocks over a beaker. The hard water, metal floor, and fumes combine to knock him out.
Miraculously, Garrick would survive the incident and would gain incredible speed that he would eventually use to become The Flash. While Garrick's origin isn't incredibly different from Barry Allen's or Wally West's lab accidents, one element makes it hilarious: the fact it all happened because he needed a smoke. Yes, it was the late '30s, but smoking alongside potentially dangerous experiments was a bad idea. But, Garrick didn't accidentally light anything on fire, he simply leaned up against a table and knocked everything over by mistake.
Garrick accidentally giving himself powers because he needed a cigarette and his general lack of awareness in a highly volatile setting makes his origin one of the dumbest in comics. He simply could have not smoked in the lab or used a table full of dangerous chemicals as a bench. Jay Garrick is one of the coolest versions of The Flash, but when it comes to his origins, his has got to rank atop the most hilarious ever.