It pays to be angry. Rovio, the makers of the popular Angry Birds game, has raised $42 million of funding from a group of leading venture capital firms, including Accel Partners and Atomico (the latter founded by the founders of Skype).

Rovio has been very successful taking a simple game concept and turning it into a successful brand across multiple devices and platforms. Everywhere Angry Birds lands, it becomes the #1 most popular game (I didn’t say best selling since it is free on Android devices).

Investors do not place bets on one game so there has got to be a bigger picture. In an article on Gigaom, Rovio says their goal is to make Angry Birds the Spongebob Squarepants for the iPhone generation. That’s a lofty goal and would be worth every penny of the $42 million invested.

It’s also quite a challenge. Spongebob is a cartoon with a storyline and backed by Nickelodeon. Angry Birds is an addictive game but the game play and storyline (pigs steals eggs, birds get angry) is not what you would call deep.

So far, Rovio has expanded to sell Angry Birds dolls and an Angry Birds movie is in the works. They also plan to release a Facebook version of Angry Birds very soon. If Angry Birds takes Facebook by storm, then it will be another big success in the building of the brand.

I have to assume Rovio plans to release a series of new games IP and try to replicate the success of Angry Birds. If they can create a bunch of Angry Birds like successes, they can then become the Nickelodeon of the iPhone generation. It’ll be impossible have another Angry Birds like hit by just throwing it up on the crowded iTunes marketplace, but $42 million in marketing should help.

The biggest danger for Rovio and Angry Birds is over-exposure for Angry Birds. The iPhone generation is a fickle audience. It would be a shame for Angry Birds to be Biebered.