On the surface, "Kung Fu Panda" is a satire of the popularity of martial arts movies that took off in the US in the 70's. However, there is also the story of a hero's quest.
That hero is Po, a giant panda (Jack Black), who is a fan of the Furious Five, an elite group of warriors who defend the Valley of Peace. He dreams of them, then deceives his adoptive father into thinking that he had the "noodle dream", meaning he would be ready to inherit the family business. While it was not outright stated in the movie that Po was adopted, that would be addressed in the sequel, 3 years later.
So Po sets out to attend an exhibition of the Furious Five, designed to determined which of them is meant to be the Dragon Warrior. However, Po clumsily stumbles into the arena, and the ancient sensei determines that Po is meant to be the Dragon Warrior over Tigress (Angelina Jolie), Crane (David Cross), Mantis (Seth Rogen), Viper (Lucy Liu), and Monkey (Jackie Chan). Some time before, a snow leopard thought he was meant to be the Dragon Warrior, but was deemed unworthy, and excommunicated, if you will, from the temple. He's broken prison, and now seeks the Dragon Scroll, which Shifu (Dustin Hoffman) reluctantly gives to Po.
The CGI animation is lush & beautiful. The script drags a little bit, though. Scope out the trailer.
As noted, a sequel followed in 2011, and led to the current Legends of Awesomeness series airing on the Nickelodeon family of networks. A 3rd movie will open next year.