An absurd response to any statement or declaration, particularly those which indicate some degree of pride or satisfaction.
First seen in the Family Circus parody site in which humorous captions are substituted for the normal ones; the cartoon was of Jeffy fishing and fantasizing about riding atop a giant fish that he had caught. The idea was apparently that the fish's poop was keeping it in place, and the "whar" was included to lend it a maritime flavor.
A: So Jessica and I went out Friday night, and we had the best time! First we went over to Jon's house, and--
B: The poop keeps it whar it is.