Inventor of the Mundane

Coffee Collar? I hear the guy that invented these gets ten cents every time one is used.

Sometimes the plot needs a character to be very wealthy without ever actually doing anything or being particularly clever. When such a thing is needed, the character will be credited with inventing something very simple, useful, and everyday. Not anything groundbreaking like cold fusion—think more along the lines of velcro.

In other cases, the character is shown to be someone who isn't necessarily a great scientist, but clever and practical minded. Perhaps the character won't get famous or wealthy off of the invention, but their product at least will be a household name.

Compare with Weekend Inventor when inventing is a hobby rather than a lucrative living. See also Bungling Inventor, Gadgeteer Genius, and Mr. Fixit. If the inventor was an ancestor, then it is Royalties Heir. If the character only claims to have invented something, then it is Invention Pretension. In a number of cases this also doubles as a Shout-Out or a Namesake Gag.

Examples of Inventor of the Mundane include:

Anime and Manga

From Akira Toriyama's Dragon Ball, Dr. Briefs invented capsules: nifty little things that defy the laws of conservation of mass in order that whatever vehicle, housing, or devices one could possibly need can be shrunk down to the size or a pill. Due to his rule as one of the series' Gadgeteer Geniuses, he fills that role a bit more than this (but the capsules are very mundane in that world).

Film

Patrick Dempsey was portrayed as one in the movie Made Of Honor. He invented that cardboard thing that goes around the coffee cup that keeps your hand from getting burned—named in the movie as the "Coffee Collar." Patrick Dempsey got 10 cents whenever one was used.
In Garden State, one of Zach Braff's friends invented "silent velcro" and became a multi-millionaire. He now spends his time driving golf-carts around his mansion.
Invoked in Romy and Michele's High School Reunion. The girls claim to have invented Post-It Notes, but it's a lie to impress their old high school peers. They deliberately tried to think of something everyone has heard of, but no-one's ever thought about who invented it.
The Social Network features the Real Life story of Mark Zuckerberg and the invention of Facebook.
In Austin Powers: International Man of Mystery during a group therapy session Dr. Evil mentions that his father claimed to have invented the question mark (among many other, equally strange declarations).
In Men in Black, the MIB owned the patents to some 'out of town' inventions. Among them was Velcro.
In Star Trek IV: The Voyage Home, Scotty hands the chemical makeup for Transparent Aluminum (which will be extremely mundane in the Star Trek canon, but isn't in 1980s America) to an engineer.

McCoy: Scotty, you're tampering with the future!
Scotty: How do you know he didn't invent it?

Flash Of Genius is a movie Based on a True Story about Robert Kearns and the invention of the intermittent windshield wiper.
In Office Space, the character Tom Smykowski uses the settlement from a car accident to fund the invention of his "Jump to Conclusions" mat ("Have a problem? Just take out the mat and jump to a conclusion!"). In universe, it was wildly successful.
In Mean Girls, Gretchen's family is wealthy because her father invented toaster strudels.
Nick Vanderpark (Jack Black) in Envy becomes rich after inventing a product that vaporises dog poo.

Literature

The father from Holes spent the entire novel trying to invent the perfect odor-eater. He finally succeeded not only at inventing it, but also at marketing.
Good Omens has a list of people who invented things that, once they were invented, became so ubiquitous no one remembered they ever needed inventing. They all have names like Device or Gadget.
One Daniel Pinkwater book featured a protagonist taking a summer job working for his uncle, who had invented the things they put on the end of shoelaces ("aglets", according to The Other Wiki, but carefully not given a name in the novel).
In Johnny and The Bomb, Wobbler is left in the past, unable to return to his time due to a paradox. While taking The Slow Path, he uses his knowledge of the present to become obscenely rich by both 'inventing' fast food chains and encouraging the inventors of other products.
In The Westing Game, James Hoo has a grudge against Westing for stealing his idea for the disposable paper diaper. He later invents a paper shoe liner, Hoo's Little Foot-Eez, that sells well enough that he retires a wealthy man.
In Dirk Gently's Holistic Detective Agency, the main protagonist invented an app that turns spreadsheet data into music, which corporations love because the resulting tunes make good jingles. He doesn't personally get rich by doing so, but it's the product that keeps his boss's software company afloat.

Live Action TV

A Running Gag from The Adventures of Brisco County Jr was the invention of now-everyday objects, some of them decades in advance of their normal time.

"It's the coming thing!"

Red Dwarf: The episode "Timeslides" features a man who became staggeringly rich by inventing a novelty stress toy, the "tension sheet". (It was nothing more than repurposed bubble wrap.)
Walden Schmidt from Two and A Half Men is billionaire after developing a website that he sold to Microsoft for $1.3 billion. No one has ever heard of it beacuse Microsoft decided to bundle it with the Zune.
The town of Neptune in Veronica Mars is so high-class because it's home to a bunch of children of the tech boom. Duncan Kane's dad, for instance, invented streaming video,

Newspaper Comics

One Dilbert strip showed Dilbert's great-grandfather as the inventor of sliced bread, the greatest thing since unsliced bread.

Video Games

In Mass Effect 2, if you ask EDI where Cerberus gets funding from, Joker says that the Illusive Man invented the paper clip. EDI helpfully clarifies, "That is a joke."

Web Comics

Otra in Girly is wealthy only because she accidentally came up with a popular clothing fashion line that only consists of wear with the number 0 on it, or letter O in reference to her name, after a designer took notice of the number 0 she drew on her own shirt and found it to be brilliant.

Web Original

Mentioned as a gag in the Legendary Frog cartoon where Kerrigan decides to become an inventor and make millions. She says to her boyfriend, "Remember John from next door? John Velcro?"

Western Animation

Time Squad had plenty of these. Whether the inventors actually got around to inventing their mundane inventions was completely subject to plot convenience.
Danny Phantom: Sam Manson's family became wealthy because an ancestor of hers invented a device that twirls toothpicks in cellophane.
- Danny's parents make a living from the inventions they make.
Kim Possible episode "Ron Millionaire" featured Ron Stoppable receiving 99 million dollars for inventing the Naco. Whatever he didn't spend during the episode was stolen by Dr. Drakken in the end.
In The Looney Tunes Show, Bugs is wealthy and living in a nice home because he invented the carrot peeler, apparently a useful kitchen appliance.
In Total Drama Revenge of the Island, Staci always talks about how her ancestors invented swimming and log cabins, among other inventions.

Real Life

Mike Nesmith of The Monkees is independently wealthy because his mother Bette Nesmith Graham invented Liquid Paper correction fluid.