Have you heard of "Streak the Wonder Dog"?

Streak an Green Lantern comics

Yesterday this blog highlighted Superman's dog Krypto. Batman also had a dog known as "Bat Hound," and as a comic book fan, I thought I knew all of the superhero dogs. However, I recently stumbled upon another called "Streak the Wonder Dog." Streak is a German Shepherd who appeared in 3 different comics during 2 years.
  I only discovered "Streak" because our friend Lynn gave me a hardbound book collection called "DC Comics: A Visual History" and the dog made his debut in 1948 and was in comics for a year, appearing several times in 1949. 

WHO CREATED STREAK? Streak was the creation of Robert Kanigher, and was introduced in the pages of Green Lantern as GL’s dog.

Streak's first appearance 1939, All-American Comics

WHERE ELSE DID HE APPEAR? Streak debuted in DC Comics' All American Comics #96 in April 1948 and issue #99 in July 1948 with the Green Lantern. He even made a cover. His next appearances were in Green Lantern comics starting with issue #30 in 1948. In fact, Streak wound up taking over the covers of Green Lantern's comic (and tossing the superhero off the cover) until issue #38, which was the final issue of the comic series. Streak was also in a three issues of Sensation Comics in 1949 which featured Wonder Woman. Streak was a back feature and never made the cover.

Streak was a back feature in Sensation Comics 1949

Streak: Credit: DC Comics