It wasn't an exact catchphrase, but a common theme of the series was that they would figure out some non-car-related thing that the person liked, and work that into the car. Then Xzibit presenting the car to the person would be like, yo, we heard that you like fish, so we installed this 20 gallon fishtank in your trunk. Thus spawned the meme.

Like the Bear Grylls thing, it's not like he drinks his own urine in every episode, yet it was enough to spawn a meme.

Maybe someone liked cars and he put a car inside their car!