In my opinion, Penny was the main hero of the yesterday's episode of The Big Bang Theory, 04x19 "Zarnecki Incursion".
Sheldon's World of Warcraft is hacked and everything, including all the gold and the battle ostrich, is stolen. Police turns out to be useless, despite Sheldon's hysteria.
...spoilers continue below...
All the boys are helping Sheldon. It turns out that Priya, Leonard's new girlfriend, has no empathy for Leonard's computer games hobby. This fact makes Priya much less suitable as a girlfriend relatively to Penny, a cured online game addict.
Howard finds out that the hacker is Todd Zarnecki, so all of them ultimately go to Carlsbad, CA to force him to return all the stolen stuff. Instead, a mean and fat Zarnecki - a Michael Moore lookalike - steals Sheldon's klingon batliff as well.
Fortunately, Leonard's car has a mechanical problem while they're on their way back. They decide to call Penny - not Priya - to pick them. Penny is clearly pleased to find out that she's closer to the boys' hearts.
When Penny learns that they didn't manage to get Sheldon's stolen virtual goods back, she decides to show them how a quest is commonly completed in Nebraska. They return to Carlsbad, CA and Michael Moore's lookalike opens the door again.
He's being an arrogant jerk again but Penny informs him that he can finally taste girl's punch in his special parts. She kicks him into his balls - LOL, Penny's kick into Michael Moore's balls was the peak of the episode for me - and "we" succeeded, Sheldon exclaims! :-)
After a painful and silent walk on the staircase with Priya, Penny finds out that Amy was right when she has logically deduced that Penny must have a desire to fling her poop at Priya.
Penny has learned a lot and, as far as I can say, she has the natural right to possess or reject the likes of Leonard. In this season, Kaley Cuoco spent much more time with the other girls. See what Cuoco has to say about this transformation of the character.