Found an interview/article with Johnny Galecki. He talks more about the shows third episode this season and what it means to Sheldon, Penny and Leonard.
Plus there is also some further information about a casting spoiler for episode 6.
"We just shot our third episode of the season," Galecki said, "and that's the one that will really start to explore what effect the relationship will have on the trifecta of Sheldon, Leonard and Penny. It was such a fun episode. Kunal and Simon have a B-story and are off at a nightclub, but the rest of the episode is basically me, Jim and Kaley on the couch talking.
"It was like theater, really, and the audience loved it. And it's my favorite episode so far this season. There's no gimmick to it. It's literally three characters sitting on a couch and dealing with this new baby elephant in the room.
"Now, as opposed to Leonard's exasperation with his best friend (Sheldon), he really has something to stand up for, and that's Penny.
"So, when Sheldon shakes things up, there's too much at stake now. There's an ounce of manhood in that, relative to Leonard in the past, and I like that."
Source ...
ALSO, a casting call for episode 6 is
here. It doesn't relate to Sheldon/Penny so much, but some people might be interested in what is coming up.