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.
Their relationship could develop through shared hobbies. For instance, if Penny starts to show more interest in Leonard's scientific work, it can bring them closer. They can have deep conversations about his research, and Leonard can teach her new things.
Imagine Penny cosplaying as a sexy character from a fantasy world. She might have chosen a costume inspired by an elven princess but with a more modern and alluring twist. Her long blond hair is styled in loose waves, and she has a tiara on her head. As she walks into Sheldon and Leonard's apartment, they are both in awe. She then starts to act out some of the character's mannerisms, like speaking in an elegant accent and making grand gestures. This not only amuses her friends but also makes her the center of attention at the little gathering they have.
A memorable moment was when they both participated in the scavenger hunt. They showed great teamwork and competitiveness, which was really fun to watch. They were able to use their different skills to try and win the hunt.
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.