This is one of the most amazing easter eggs in GTA V. It is based after a popular video posted by a crazy happy guy in 2008 shortly after GTA IV was released. Now in 2013, R* recognized the video and bought this to GTA V. At one time, when switching to Trevor outside missions. He will be in a highway pursuing a scooter, screaming the same quotes like the happy guy playing GTA IV.

You can see a detailed video about this easter egg here below:

GTA 5 - Easter Egg 7 - Scooter Brothers!01:42

GTA 5 - Easter Egg 7 - Scooter Brothers!