Welcome to Just Answer and thanks for your question. The song was "Hang On" by Smash Mouth.
I know it's on the CD "Get the Picure." You can check itunes for a download of just that song if you don't want to buy the rest of the CD.
Smash Mouth is a pop rock group. Some of their other songs you may remember are "Walkin' on the Sun" and "All Star." They've also done lots of songs made popular by other artists including "Why Can't We Br Friends?" "I'm a Believer" etc.
You are mistaken. The song is "Hang On" by Smash Box in the Cat in the Hat.
The answer is right. I've looked at the movie, as well as the dozens of copies of that bit on the internet.
I am going to opt out since you won't believe the truth and I don't have time to argue with you.
I believe the the song you are looking for is a song by Smash Mouth ("Getting Better") using David Newman's score in Cat In The Hat. Paris Hilton was a Female Club Goer in the movie. The original song was done by the Beatles and remixed for the movie: This is the Beatles version: http://www.youtube.com/watch?v=lRL00smhmc4&feature=related
This is a link with all the sound tracks that you can hear each song: http://www.amazon.com/Cat-Hat-David-Newman/dp/B0000DZE4X