First Appearance: Adventure Comics #293 (February, 1962)
Publication History: The Legion of Super-Pets is a fictional team of super-powered pets in the pre-Crisis DC Universe. Members include Krypto the Super-Dog and Streaky the Supercat. The team first appeared in Adventure Comics #293 (February 1962), though most of the members had appeared in earlier issues. Significant appearances during the Legion's Adventure Comics run include issue #322 (July 1964) in which Proty II is initiated onto the team; issue #343 (April 1966) in which the Super-Pets help the Legion battle the Luck Lords; and issue #364 (January 1968), "The Revolt of the Super-Pets!" The team only rarely appeared after the Silver Age and have not made any appearances post-Crisis, though Krypto has become a supporting character in the Superman titles.
Origin: The alien creatures known as the Brain-Globes of Rambat decide that in order to succeed in their plan to move Earth to their own solar system, they must defeat Superboy. When they are unable to gain control of Superboy, they summon Cosmic Boy, Lightning Lad, and Saturn Girl of the Legion of Super-Heroes from the future and mentally command the trio to capture him. After Superboy is defeated, the Brain-Globes of Rambat release their hold on the Legionnaires. When they notice that the Brain-Globes cannot control animals, the Legionnaires gather Krypto the Super-Dog (from Superboy's present), Streaky the Supercat and Beppo the Super-Monkey (from Superman's present), and Comet the Super-Horse (from a few weeks in Superman's future) to battle the aliens. The pets defeat the aliens and are named the Legion of Super-Pets, the animal branch of the super club. They are then returned to their proper time periods. Proty II would later join the team.
Krypto the Super-Dog: Kal-El's puppy, Krypto, was lost in space before the destruction of Krypton. After Kal-El grew into a boy, Krypto found his way to Earth and the two were reunited. (Adventure #210)
Beppo the Super-Monkey: Beppo was a lab monkey of Superboy's father, Jor-El. The monkey stowed away aboard Kal-El's rocket and plagued the Boy of Steel with much mischief. (Superboy v.1 #76)
Comet the Super-Horse: Circa 1000 BCE, a centaur named Biron was granted super-powers by the sorceress Circe. But Circe's enemy, the sorcerer Malador, transformed Biron into a horse and banished him to a planet in the constellation Sagittarius, where he remained for almost 3,000 years. Biron was freed from his imprisonment by Kara Zor-El's passing rocket ship. He then followed her to Earth, where she became Supergirl and named him Comet. (Action #292; 1st app. Adventure #293)
Streaky the Super-Cat: Supergirl's Earth cat Streaky became a Super-Cat through exposure to a newly created Kryptonite isotope called X-Kryptonite. (Action #261) Supergirl later met Streaky's descendant, Whizzy, in the 30th century. Whizzy was never a member of the Super-Pets. (Action #287)
Proty II: a small amorphous creature from Antares II. The Super-Pets met Proty II when they were asked by the Legion to guard the Legion clubhouse. Proty recounted how the his race gained their shape-shifting abilities centuries ago. He underwent a series of trials to prove his worthiness and joined the Super-Pets. (Adventure #322) NOTE: Read more about Proty's race. Proty was introduced to the Legion as Chameleon Boy's pet (Jimmy Olsen #72) but it was soon clear that his race were fully sentient, and far more intelligent than normal Earth animals. Like his predecessor, he was selfless and quick to enter dangerous situations. When one of Triplicate Girl's three bodies was slain by Computo, Proty II attempted to distract Computo by posing as the Weirdo Legionnaire. (Adventure #341)
Fun Fact: The Legion was parodied in an episode of Robot Chicken. Comet, Streaky, Krypto, and Beppo appear, along with "Hissy the Super-Snake". Superman returns to the Fortress of Solitude from a month in space to find the pets have all frozen to death because their babysitter mistakenly thought she was watching them the month after.
Fun Fact: The Legion of Super-Pets (Beppo the Super Monkey, Streaky the Super Cat and Krypto the Super Dog) appear in the DC Nation Superman 75th Anniversary short that was shown at New York Comic Con 2013 and will be included in the Man of Steel DVD.