Superman was used to Batman's constant attempts to forge a "closer" bond, so he played along with Batman's ruse here. For God's sake, a slide projector. He must have been up all night cutting out pictures of himself and pasting them into other pictures. He left knowing that Batman would feel very proud of himself, and pleased with what he'd made Superman think - and then Batman would realize that Kryptonians wouldn't write English on a slide, and he spent the night pacing the Batcave beating himself on the temples with his fists, saying stupidstuipidstupid. Superman knew Batman would make a joke about it the next day - hah hah, fooled you! - and they'd laugh and it would never be mentioned again. It was just sad. Superman only hung out with him because he felt sorry for him. Oh, he did okay, but he thought they were on the same level, or something. Superman could have killed him in a second with eye-rays. Once he sneezed and gave Batman a concussion that made him smell burning pencils for three weeks. A few months later Batman sneezed really hard and Superman pretended it knocked him back in his chair. It was just pathetic. He had to find a way to start saying no when Batman called to go do something. Did they only call each other "Clark" and "Bruce" when they were out of costume? Was that the rule?