It wasn't everyday (or every night) that you saw Batman being bested. But that's exactly what Superman saw on that fateful night when he first met Catwoman. She had stolen a hard disk from Lex Luthor's home for the Justice League. And now she was running off with that same disk. At first it didn't look very promising for Batman. She was clearly faster and better at parkour, and Superman wondered if he should step in. But then she came to a sudden halt. Finally Batman caught up to her. She handed the disk to him and her smirk told Superman she had enjoyed riling up the Dark Knight.
This was quite curious. Most criminals were terrified of Batman. But here was the World's Greatest Thief and she clearly amused herself by getting him to run after her. She get closer to Batman and whispered to him. Superman didn't usually eavesdrop on private conversations but this time he couldn't help himself. She told him "don't look like you didn't enjoy it handsome. I figured you'd be bored out of your mind in Metropolis and thought I'd get your blood pumping"
"Did you now?" Batman asked. His voice sounded almost humorous. "How thoughtful."
"Hit me up as soon as you come back to Gotham. And I'll REALLY get your blood pumping" Catwoman told him as she gently scratched his cheek with her titanium claws. Then she leapt off the edge and was swinging her way to the La Meridien Hotel. Superman couldn't help but notice the way Batman's heartbeat and his breathing sped up when she was close to him. Particularly when she ran her claws over his skin. He didn't want to pry but this was just too intriguing.
"Umm...you wanna tell me what the hell that was?"
Batman completely ignored the question. Instead he simply stared ahead in the direction in which Catwoman had gone and touched the part of his cheek that she had scratched. You'd have to be blind to not to see just how he was affected by her.
Superman was equally intrigued by Catwoman. Here was one of the world's most wanted criminals. A woman who had been wrecking havoc all over North America and Europe. A woman who made fools out of every major police force in the two continents. And yet, anytime she was asked to help the Justice League, she always stepped up. Granted she did get up to a bit of mischief each time, but in the grand scheme of things it didn't do any harm.
Superman suspected that she wasn't really a bad person. Otherwise Batman wouldn't have trusted her. In time, he learned her true identity, that she was the high flying, globetrotting entrepreneur/socialite/philanthropist Selina Kyle. She too figured out that Superman was actually mild mannered reporter Clark Kent. They often met as civilians. Usually at the Wayne Manor. Clark found that he really liked talking to her. Like Bruce she seemed well versed on a number of subjects and unlike Bruce she was an excellent conversationalist. Her wit was deadly and her sarcasm, biting. But underneath that "devilish" exterior Clark could see that she was quite down to Earth and thoughtful.
Clark noticed just how calm and happy Bruce was when she was with him. He would watch as he danced with her at his galas. The way he held her in his arms as if she was the most precious being on the planet. The loving look in his eyes and the sheer chemistry between them told Clark that she was much more than "just an ally" as Bruce had told him.
When Bruce survived an assassination attempt by Deadshot, it was Selina who ran after the hitman. And it was she who took charge of Bruce's care and safety. What Clark found even more remarkable was the way the Bat family willingly followed Selina's lead in this matter. They trusted her, just as much as Bruce did.
Clark's suspicion that Catwoman was as much a hero as he was, was confirmed when she decided to infiltrate Darkseid's ship to help League members escape. The ship's insides were lined with Kryptonite. And Batman and Wonder Woman were already occupied dealing with a horde of Parademons descending upon Gotham. Just like Batman would, Catwoman had simply made the decision that she must risk death, or worse, in order to ward off the attack. The matter of fact way she told Superman had touched his heart and he was overcome with admiration for her.
Catwoman snuck into the alien spacecraft, figured out how to dismantled its superior security systems, snuck past those on board and did exactly what she said she was going to do. Superman was just starting to worry when she along with Green Arrow, Black Canary, The Flash, Green Lantern, Cyborg and several other heroes emerged from the craft. Superman had to restrain himself from applauding.
It was not Catwoman's only contribution to fighting off the invasion. Superman later learned that she also risked her life to save countless civilians. And after the invaders retreated, Selina Kyle had allowed those who were worst affected to stay in the buildings that she owned, rent free. When Clark told her what a wonderful thing she had done, she tried to downplay her goodness. She just shrugged and said "meh! I don't think I want to deal with the upkeep of those buildings. If people live there, at least they'll keep them clean", before quickly changing the subject. Clark smiled to himself. Reluctance to admit that they were, in fact, good people was definitely a trait the Bat and the Cat shared.
Fighting together had brought Clark and Selina closer. They talked often and would bond over their love for literature and art. When Clark wrote a piece about corruption in the art world, it was Selina Kyle he first contacted. She gave him information and shared insights into the business of fine arts that none of his other sources could have given him. He was truly blown away as Selina revealed the rot that ailed art trading.
"Art, today, is becoming a way to launder money", Selina told Clark as they sipped coffee in an upscale restaurant in Metropolis "Rich people will buy mediocre pieces for millions and then they "donate" them to galleries in order to get a tax deduction. These assholes could be paying their taxes that can pay for better healthcare in this country but they'd rather get their fingers into the art world. Thereby harming the economy and upcoming artists."
She also gave him the names of seemingly respectable business people and several criminals, including assassins, mob bosses who engaged in this sort of manipulation. Clark began working on his piece with renewed vigour and it ultimately rattled quite the hornet's nest, and it also got Clark a Pulitzer Prize. He wanted to thank Selina but, as always she dismissed her own contribution and said to him "don't sweat it Boy Scout. Just make sure they mention how gorgeous my dress is any time I attend an even in Metropolis."
Clark also watched Batman and Catwoman's love grow and blossom right before him eyes. Bruce had build walls around himself and so did Selina. It seemed fitting that they'd only drop their guard with each other. She made him less intense, less tightly wound. And he had made her believe in her own goodness and embrace her role as a hero. Gotham's Dark Guardian Couple made one hell of a team. When they first became friends, Bruce told Clark that he wasn't meant for a relationship as he didn't want to endanger any woman. This clearly wasn't a problem with Catwoman. She was Batman's equal and could protect his body and his heart.
Clark loved Bruce like a brother. Knowing that he was with a woman who gave him such joy was one of the things that helped Clark sleep peacefully. And in Selina Kyle, Clark Kent too had found a friend for life.