When Bryan Bundesen posted a photo of his sister’s kitten on Reddit, little did he know that the odd-looking feline would become one of the internet’s best-known celebrities.

The sourpuss image has been replicated thousands of times with grumpy captions posted on websites and social media pages. She has a manager, a successful merchandising franchise, a Grumpy Book, a Facebook page with almost seven million likes and nearly 250,000 followers on Twitter. Now there’s a movie, Grumpy Cat’s Worst Christmas Ever, to be broadcast on the cable TV network, Lifetime.

"Grumpy Cat is phenomenally successful,” says Karen North, a professor of social media at the University of Southern California's Annenberg School.

"One of the most popular activities online is displaying images with snarky captions. People take an event or a piece of media or an image on a digital platform and they mash it up, or they parody it or they adapt it."

For this, Grumpy Cat is the "perfect image”. Her 15 minutes of fame has transformed her into a marketing and entertainment powerhouse. She is an internet celebrity that now rivals other iconic figures such as Garfield and Hello Kitty. But is she immortal?