If Penny does make more money than Leonard, then it definitely feels like it restores the balance between the two, as their relationship often feels weighted in Leonard’s favor. When the two first meet, Penny is a struggling actress who, much to Sheldon Cooper’s (Jim Parsons) dismay, uses Sheldon and Leonard’s wifi and frequently eats meals at their (larger, nicer) apartment for free. She might be beautiful and socially adept, but she basically depends on Sheldon and Leonard for key aspects of her survival at first … and the show often highlights the fact that Leonard considers himself to be much, much smarter than Penny and makes no secret of that.
A perfect example comes in the Season 6 episode “The Extract Obliteration,” when Leonard discovers that Penny has been quietly attending classes at community college (Leonard has a PhD, while Penny never graduated from university). As it turns out, Penny had a good reason for keeping this from Leonard, because when he sees one of the papers she’s written, he hastily rewrites it to help Penny get a better grade instead of encouraging her to learn on her own. It’s a pretty condescending move on Leonard’s part, so the idea that Penny ultimately surpasses him financially helps soften that blow somewhat.
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