The Internet isn’t easily shocked. But when reports began to surface that famous internet feline Grumpy Cat had earned $100 million for her owner last financial year, office workers around the world clutched their favourite coffee mug just a little tighter.

The indignant op-eds soon followed. How exactly had Grumpy Cat, aka Tardar Sauce, turned a genetic defect and a persistent frown into an online empire? Why was this cat earning more than Leonardo Dicaprio and Rihanna combined? Who was in charge here?

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When the cat’s owner, Tabatha Bundesen of Arizona, fronted the media soon after, she described the claims as “completely inaccurate”. Her vague choice of words did little to simmer down the financial speculation, but the corresponding articles did shed light on the mysterious world of famous pets.

And the guy pulling strings behind the scenes, Ben Lashes – Internet Cat Agent.

A failed musician from Seattle, Lashes got into artist management, and had his big break helping the owner of Keyboard Cat negotiate licensing deals. When the first images of Grumpy Cat started being shared online in 2012, he was on a plane and waving contracts around within days.

Grumpy Cat and her owner, Tabatha Bundesen. Photo: Getty

Three years later, Grumpy Cat’s likeness has been used to sell a line of iced coffee called Grumppuccino, she’s made guest appearances at Music Festivals, is “the face” of Friskies cat food, has a number of books, and more merchandise than we can be bothered listing. There’s even a movie, Grumpy Cat’s Worst Christmas Ever.

While all the above probably isn’t worth $100 million (minus Lashes’ 20 per cent cut), it definitely adds up. And as Bundesen pointed out in an interview: “I was able to quit my job as a waitress within days of her first appearance on social media, and the phone simply hasn’t stopped ringing since.”

For those who have similar ambitions, a number of books are on the market to help you turn your otherwise useless pet into a lucrative gold mine. In the meantime, here are the five most prominent.

Maru

One of the first ‘Internet Famous’ cats to branch out into licensing deals, Maru is a Scottish Fold from Japan. His owner started posting YouTube videos in 2009, and since then they’ve been viewed over 250 million times, generating about $180,000 annually via YouTube’s partner program. Associated merchandise, including a very popular book, and various endorsements in Japan, have enabled Maru’s owner to live very comfortably off a cat that just likes to sit in boxes.

Fun Fact: Maru once had the seventh-most subscribed YouTube video channel in Japan.

Colonel Meow

Sadly deceased, Colonel Meow was a Himalayan–Persian crossbreed who came to prominence in 2012 after his owner posted a number of photos on Instagram and Facebook. With his ridiculously long fur and fierce expression, he built up a legion of online followers before dying from a heart condition in 2014 aged two. The Colonel may be in a better place these days, but his videos still earn around $5000 annually via YouTube.

Fun Fact: Colonel Meow holds the world record for the longest fur on a cat (nine inches, or about 23 cm).

Boo, The World’s Cutest Dog

Boo’s owner is a Facebook employee who created a page for the Pomeranian back in 2010. His online popularity soared when Ke$ha (at the height of her popularity) tweeted a message saying she had a new boyfriend and linked to Boo’s FB profile. The page quickly hit five million followers and the dog was offered a publishing deal – that book has now been printed in 11 different languages, and Boo is the ‘spokesdog’ for Virgin America Airlines. He generates approximately $1 million in revenue every year.

Fun Fact: With 17 million Facebook followers, Boo has more online friends than everyone else on this list combined.

Henri, le chat noir

‘The Existential Musings of an Angst-Filled Cat’ have earned ‘tuxedo cat Henri’ a considerably online following. His first video was released in 2007 as a one-off, but it would take another five years for the world to finally take notice and the web hits to start piling up. Since then several short features have been made, winning praise from online stoners, philosophy majors, and film critics alike – Roger Ebert described Henri 2, Paw De Deux as “the best internet cat video ever made”.

Fun Fact: Henri’s owner makes around $1000 a week in merchandise sales from his online shop.

Lil Bub

A master class in turning a physical defect into a money spinning venture, Lil Bub’s short lower jaw and protruding tongue earn her owner, Mike Bridavsky, around $30,000 a year in YouTube royalties. But the serious money is in guest appearances, merchandise, and income from Lil Bub’s documentary (Lil BUB & Friendz), which was produced by Vice Magazine, and won Best Feature Film at the Tribeca Online Festival in 2012. Although the official figures are never disclosed, Bridavsky has donated at least $200,000 to pet charities, and quit his day job a couple of years back. Which would strongly suggest an income north of $1 million.

Fun Fact: Lil Bub launched her own talk show host in 2013 (don’t ask), and the first guest was Whoopi Goldberg.