As I sit here and type this, I haven’t seen the DC League of Super-Pets movie. But that group, at least as a concept, has actually been around for awhile even if the majority were basically all Superman-style characters who just happened to be animals, and all incarnations were led or at least headlined by Krypto the Superdog.
However, one of the more prominent members of that group is clearly absent from the movie, and that would be Streaky the Supercat because if you’re going to have a super-dog, then a super-cat is pretty much a given.
Streaky, first appearing in February 1960’s Action Comics #261, was not a refugee of the planet Krypton. Yes, while Krypto came from Krypton, Streaky began life as an ordinary stray cat from planet Earth. But this was the Silver Age, so kryptonite came in a wide variety of colors and with a large range of effects. One such kryptonite was X-kryptonite that could give animals temporary superpowers like the sort that any Kryptonian would have. Streaky was exposed to a piece, flew around doing what a cat in a comic book aimed at kids would consider good deeds, and eventually the powers wore off and he started to fall from where he was flying…which was outer space.
Fortunately, there was a superhero flying nearby in the form of Supergirl to catch him and take him back to the orphanage she called home because Superman just left his teenage cousin there to live there in secret under the idea the rest of the world wasn’t ready for her yet. From there, Streaky would from time to time be exposed to more X-kryptonite, temporarily gain powers, and do the superhero thing, even teaming with Krypto and the other Super-Pets.
That all ended around 1970 when DC’s higher ups temporarily got rid of all kryptonite. That meant Streaky basically just became an ordinary housecat.
However, this is DC, so there would always be references and callbacks. Post-Crisis, various cats that apparently all named Streaky would show up. Supergirl herself had a couple in different incarnations, at least one getting the name because she (and Streaky was now a “she”) kept missing the litter box. Post-Rebirth, a superpowered Streaky did appear in a Super Sons Annual, along with the rest of the Super-Pets in its more modern incarnation, meaning a number of Damian Wayne’s pets were there.
That said, Steaky has made a number of appearances in animation, mostly silent cameos and the like where the cat wasn’t really named, but it was obviously him or her since it would always be an orange cat with a patch shaped like a lightning bolt on the side. The most prominent, and the only time Streaky was referred to by name, was on the animated series Krypto the Superdog where Streaky was basically Krypto’s sidekick/partner.
So yeah, if Superman can have a flying dog, Supergirl can have a flying cat. Because, you know, Silver Age.