As far as I can remember, there is no such Penny wedgie incident in The Big Bang Theory. The series was filled with different kinds of comical situations. For example, there were Sheldon's idiosyncrasies, Howard's attempts to pick up women, and Raj's selective mutism. But a wedgie incident for Penny just doesn't seem to be part of the storylines.
A lot of fanfiction could explore Penny's emotions during her pregnancy. She might be excited but also a bit scared. In the fanfic, we could see her relying more on Leonard for emotional support. And the gang could throw her a really special baby shower, filled with nerdy and fun elements, like Star Trek - themed baby clothes or a cake shaped like a scientific formula.
Well, Penny's weight gain in The Big Bang Theory wasn't really a major plot point. But we can assume that as she got older and perhaps more settled in her life with Leonard, she might not have been as strict about her figure as she was when she was a struggling actress. There could have been times when she indulged in the guys' junk food, like Sheldon's favorite take - outs. It was more of a subtle thing, and the show mainly used it to show that she was a normal person going through normal life changes.
Penny's friendship with the whole gang is a great storyline. She is often the bridge between the nerdy guys and the more 'normal' world. For example, she helps them with social situations and they, in turn, help her with things like knowledge and different perspectives.
There are no such inappropriate stories in the official plot of 'The Big Bang Theory'. The show mainly focuses on the nerdy and humorous interactions among the characters, their friendship, and their romantic relationships in a family - friendly way.
One common theme is the growth of their relationship. Their friendship or potential romantic relationship evolving over time, with Penny helping Sheldon become more social and Sheldon introducing Penny to new intellectual concepts.
There might be a fanfiction where Penny is pregnant and she starts to feel really isolated because she's the only one in the group going through this. She misses her old life a bit, and the story could be about how she overcomes these feelings with the support of her friends and Leonard. It's very emotional as it deals with her internal struggles.
There are many possible fanfictions on this topic. One could imagine that in the fanfiction, Penny's pregnancy might bring a new dynamic to her relationship with Leonard. For example, they could become more protective of each other and start planning for their future as parents more seriously. It might also affect their friendships with Sheldon and the others. Sheldon, who is not always good with changes, might initially struggle to adapt to Penny being pregnant and the new baby in their lives.
One positive change was her growing acceptance of the guys' geeky interests. She started to enjoy things like comic - con and science - related stuff. Another was her becoming more responsible, like when she got a better job and started to manage her money better.