Hot Diggity Dog!
The expression hot diggity dog! reportedly dates back to 1928, when Al Jolson was recorded saying: "Hot diggity dog! Hot kitty! Hot pussycat! Didn't I tell you you'd love it?” after a performance of the tune "There's A Rainbow Around My Shoulder.”
While that song was about rainbows, not dogs, the song “Hot Diggity (Dog Ziggity Boom)” was popularized by Perry Como in 1956.
It definitely didn't end in the 50s. Google “hot diggity dog” and you’ll find a wide range of images, products and restaurants.