Protectors and their Prolific Pooches

Pooches that are faithful to their masters... not so hard to fine. Canines that are courageous... also pretty common. Dogs that display mental acumen rivaling humans in intellect? That's very rare.

Rex the Wonder Dog was the star of Earth-One's K-9 Army Dog Training Corp operating during World War II. Working alongside red haired Lt. Dennis (later Major Dennis), eventually Rex was adopted into the Dennis family and befriended the Major's son Danny. The Wonder Dog had several adventures around the world with both his masters, and gained relative immortality drinking from a fountain of youth.

Streak the Wonder Dog was the pet of Alan Scott aka Green Lantern of Earth-Two. Having a series of adventures, both with his costumed owner and on his own when he was later separated from Scott, Streak proved as equally resourceful as was Rex. However, he never had opportunity to meet Dennis' counterpart on his world in Donald Richards. This was left to another pooch on his world.

Thor the Thunder Dog was a canine assigned by the alien androids known as the Manhunters to their first human recruit of Earth-Two, Donald Dan Richards. A police officer wanting to make a difference, the red haired Richards found as the Manhunter not only a reliable ally in Thor but an intelligent and seemingly immortal companion. Turns out the Thunder Dog was an android himself working secretly to monitor his master for his creators. When both crimefighter and canine left for Earth-X, Dan unwittingly played into the hands of his former robotic masters. 

Thor and his fellow Thunder Dog models mirrored the robot duplicates of Krypto the Super Dog, whom his master Superboy built. The original Krypto had adventures by Superboy's side or on his own, in the 20th Century and the 30th Century with his fellow Legion of Super-Pets. His Earth-Two counterpart Thor was later given to Clark and Lois Kent by Clark’s former fellow All-Star Squadron teammate Dan Richards. Thor traveled with the Kents to the planet Telos during their stay on that alien world for a year during the Convergence event effecting cities from multiple Earths of the Multiverse.