The initial pilot featured a more conniving Penny played by a different actress. The focus group feedback was "Someone keep that mean girl away from those sweet boys".
Think of it as a show for moms / grandmothers / aunts of nerdy men. They want to see them get up so some shenanigans but generally be OK.
It's also a low effort show to watch so you can throw it on in the background while you're doing other things.