And afterward, many, many other people started not existing.
Nokia started as a Finnish company that made galoshes and rain coats. Now they are a world famous cellular company.
The first NYC marathon had 127 runners and there was a $1 entry fee. I’m not sure if that is very, very small, but it seems pretty small to me when you compare it to what it is today.
Me.
Originally I was just two cells, all alone in a uterus. But look at me now!
As best as I can tell you’re just some pixels on a monitor. More impressive than two cells to be sure, but lets not blow things out of proportion. 
I think Microsoft counts. Bought DOS for about 40,000 grand and turned themselves into am industry leader.
Nintendo started as a Japanese playing card company. 84 years later, they entered the video game market and by 1986 they had revolutionized arcade video games and home gaming consoles.
As was the character of Carol Hathaway, in ER, but audiences liked her, so she stuck around, had the central romance of the show in its heyday and Julianna Margulies won an Emmy and six SAG awards for the role.
Also starting small and becoming huge: IKEA. It started as the one man business of a 17 year old in the middle of World War II. That 17 year old is now one of the (if not the absolute) richest people in the world, and there are IKEA stores in 25 nations.
Bumping my own thread with a menton of Hannibal Lechter. The guy was a minor character in Red Dragon. It was only with Silence of the Lambs and especially the movie that he became a pop culture icon.
Basically, everything that ever became huge.
Pixar. Originally a small studio that sold computer hardware, that allowed tiny bits of animation in order to move their product. Now… well, Pixar.
I bet the people who discovered the Jochimtaler mine never would have guessed that the name would eventually become the word for US money.
Robert Crumb sold the first issue of Zap out of a baby buggy while standing at the corner of Haight and Ashbury.
The world of comic books is full of stories like these. Couple of examples:
The Tick. A guy named Ben Edlund used to doodle The Tick in the margins of the monthly newsletter from New England Comics, a Massachusetts comic book warehouse. He became a sort of secondary mascot (the primary mascot was a hairy-armed apelike thing), and people liked him, so NEC let Edlund sketch out a three-page Tick story for the newsletter one month. It was popular enough that NEC decided to actually publish a full comic of The Tick on their own, the first comic book title they’d ever actually published. From the first limited print runs, the books ran through nine printings, spawned an animated TV series, a live-action TV series, various merchandising such as action figures and clothes, and even a couple of fast-food giveaways. Not too shabby for a little doodle.
The Goliath of them all has to be Teenage Mutant Ninja Turtles. Self-published by Kevin Eastman and Peter Laird, funded by a tax refund and a loan from an uncle, the first issue of TMNT consisted of 3,000 black-and-white issues on cheap, oversized newsprint. Without coming right out and saying it, Eastman and Laird tied the Turtles’ origin into the origin of well-known comic hero Daredevil. The ad they placed in the Comic Buyer’s Guide paid off; ninjas were hot, and soon the Turtles were so popular, they inspired parody comics, few of which ran more than one issue. Some titles I remember were: Adolescent Radioactive Blackbelt Hamsters, Pre-Teen Dirty-Gene Kung-Fu Kangaroos, Colossal Nuclear Samurai Bambino Snails, and (my favorite) Geriatric Gangrene Ju-Jitsu Gerbils. The Turtles shot past parody into animated TV shows (three series so far), blockbuster movies, toys, video games, party decor, clothes, and whatever else you can imagine. On the way, the Turtles transitioned from their gritty beginnings to a more kid-friendly version, bumping profits from the billions into the squillions.
My daughters and I met Stephenie Meyer when she visited our local bookstore to promote her second book in the “Twilight” series.
And you know what? Kitty-shaped waffles are awful damn tasty. I do think the popcorn popper and the cereal dispenser are a bit much, though.
Started small, became damned-near forgotten, now is considered the one of the (if not THE) greatest composer of all time.
ETA: What do I win? 
And the vibrator is way out in left field…