A very unhappy second birthday for Grumpy Cat, the web sensation

Watch out world: Grumpy Cat has hit her terrible twos.

As expected, the internet sensation - known for her down-in-the-mouth expression and slightly bulging eyes - remained looking unhappy on her birthday on Friday while touring New York City with an entourage worthy of Hollywood.

And Hollywood is where the sour-looking feline is bound, with a film deal in the works to add to her many endorsements and licensing deals that include her scowling face on limited-edition bags of Friskies Party Mix treats and her own "Grumppuccino" bottled coffee drinks.

So who will voice the cat we love to caption? Grumpy's not saying, nor are her humans - the brother-sister team of Tabatha and Bryan Bundesen.

With her own agent, YouTube videos that have attracted millions of hits, T-shirts, calendars and a best-selling book available in 14 languages, exactly how much is this cat worth?

"The business is doing very well," Bryan laughs. "Grumpy doesn't like to discuss specifics." The humans, to be sure, are more than a little grateful.

"We both were blue-collar people," Bryan says - he was laying cables for a cable company in Ohio and she was a waitress at a Red Lobster restaurant near her Morristown home, in Arizona.