Hot Diggity Dog!
A variation of the interjection Hot dog!, hot diggity dog is an expression of joy or surprise recorded as early as 1923.
Legendary performer Al Jolson is famously said to have uttered "Hot diggity dog! Hot kitty! Hot pussycat! Didn't I tell you you'd love it?” after performing "There's A Rainbow 'Round 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.