HAPPY BY PHARRELL WILLIAMS

Hi!! What´s up?? Boys and girls: I love this song! When you are sad, when you are tired, when it seems that  you´ve got too many problems...just play the song, sing and dance...You´ll see that you´ll certainly feel better. We´ll work with it in the class. I hope you enjoy it!
This is the official video.

And here you have the lyrics in English and in Spanish.