That's a direct quote from Barney, in Back to Nature, when he comes back from his nature studies.

That moment at the beginning of the episode when Barney says he can see still see the scratch on the squad car. I don't see how. The fuel fill is on the back of the car probably behind the license plate as we see later in the episode Gomer the house guest, where Wally is putting gas in the car and it's definitely in the back.