They grow up so fast, don't they? We're of course talking about all those Angry Birds and thieving pigs who collectively turn two years old today. That's right, it's been 24 months to the day since the masses fell in love with Rovio's instant classic, and this love affair has led to the destruction of countless pigs and structures, we don't even want to attempt to calculate the wasted man/woman hours and lost productivity that Angry Birds has claimed.To celebrate the occasion, Rovio is serving up 15 new birthday cake levels, new menus and graphics, and special birthday achievements. There's more."As a birthday gift to our fans, all episodes are now unlocked!," Rovio announced in a blog post. "Also make sure to check out our new Rovio channel, which gives you instant access to your favorite Angry Birds content."If you happen to be out and about looking for stocking stuffers, Rovio says Toys 'R' Us is offering 25 percent off Angry Birds plush toys plus a code that unlocks an Angry Birds Google Chrome bonus level.