For who Katie is, I'm going with the "WTF!?!?" guess: it's Joe. Here me out: How can it be Joe, he wasn't there? Well what if he was there and just wasn't shown on camera. When ever their's character missing in an episode, I always assume that they're there, but they're just not shown on camera. As people have said, he hasn't had any story lines this season, so what if Ryan Murphy wanted to just have this big wtf moment similar to when Dave kissed Kurt with him? Finally, when they were going through all the people, everyone was mentioned, even, except for Joe. I mean a Christian guy having feelings for another guy? Sounds very Glee to me. But in the end, that probably won't happen, and it will be someone boring like Brittany.