We all know that there are people out there-whether we are one of them or not-that want Penny and Sheldon to get together. I myself am not one of them, but the purpose of this is NOT to bash those who are. I’m simply giving my theory as to WHY those people see that type of chemistry.
I’ve always loved the Penny Sheldon relationship as it is-friendly rivalry. I was shocked when I first started hearing about the people who want them to hook up. Sheldon seems so incapable of empathy, sincerity, or love. And yet, despite all that, people are seeing “Shenny.”
I’ve watched a lot of behind the scenes clips and watched and read interviews with the cast. I mean a LOT. I am pathetically obsessed. But all those hours watching the actors as themselves has made me notice something that I’ve only heard mentioned a few times. I could be totally wrong about this, but I think that what people think is “Shenny” is actually “Kim.” It seems to me that the actors have the chemistry that comes out in their characters. I’ve heard a few people mention on youtube and imdb that they think that Kaley Cuoco and Jim Parsons like each other-and I think they might be right. It’s just another theory, but I think that “Kim,” is what we are seeing, and it comes across as “Shenny” because not everyone wastes as much of their time as I do online. 
Of course I have no way of knowing if there REALLY is anything between Cuoco and Parsons, and my mind could be running along that track in my attempt for an explanation of the Sheldon/Penny shippers. But does anyone else share my opinion?