This is the song Stewie performs after Brian calls him a douche in the episode
Ocean's Three and a Half.
Then Brian comes in and I change up the tempo
Brian comes in and I change up the song
Looking at me like he thinks I'm a douchebag
But he's gonna learn pretty fast that he's wrong
Why are you bringing me down, man?
Why are you bringing me down?
Don't bring me down!
(On the last line do a hard strum with each word)
Enjoy.