Younger Caleb was all about the team sports; he played football/soccer (striker) for a while in his pre-teen/teen years, but stopped when he moved to Brooklyn. After that he was more withdrawn and prone to isolation. Still watched the World Cup matches, though. I don't imagine he'd be entirely averse to learning more about Australian-rules football/rugby, especially if he has a particularly persuasive close friend from childhood he's reconnecting with. :] Could be they ran into each other a few years back when both were freshly back? Heck, might even work out that Cooper was the one who told him about his parents' change of suit when he came back to the Deck looking for them?

As for Katya, they're definitely at least passingly familiar. Perhaps they've crossed paths while running. If she has flirted, he probably hasn't noticed; he's kind of oblivious about romantic advances, and generally takes people at face value ("This boy told me I was pretty today" meaning "Do you think I'm pretty too?" and his response being "That's nice" meaning "what does that have to do with anything we were saying?" etc.). So unless she was like, "You. Me. Naked. Now" he likely didn't get the hint. So there's that?