One Panel #841: The Earth-2 Rex the Wonder Dog

From Mister Terrific: "The Case of the Unhappy Dog" by Ted Udall and Harold Wilson Sharp, Sensation Comics #16 (April 1943)

Well, the Collie is called Rex, so why not? Where's Roy Thomas on this issue? He helps Mr. Terrific solve a case, makes the big bruiser trip before he can shoot the hero, and then drenches the crooks in wet dog. If that's not a Wonder Dog, then what is?