Penny was amiable, excitable, kind and curious. She showed a distinct lack of social awareness, likely due to not having a lot of experience with human nature. When Ruby made an unconditional offer of friendship, Penny seemed both immensely pleased and somewhat surprised. Another small quirk is that Penny hiccuped whenever she told a lie.

She also seemed to place great value on friendship, for she is greatly angered at the sight of Ruby getting knocked down by Roman's flare in "Black and White". She also placed trust in Ruby based on the latter promising that she is her friend in "A Minor Hiccup".

Furthermore, Penny seemed to be immensely curious. Upon hearing that Blake has run away, she asked Ruby numerous questions, all related to Blake and friendship in general. Despite being told not to wander off, she still wandered Vale on her own.

Penny showed insecurities about her artificial nature. Upon confiding in Ruby that she is a synthetic being, Penny was worried about how she would take the news. However, after seeing Ruby take it rather well, she was glad that Ruby did not care she was a machine, for what matters is her heart and soul.

In "Dance Dance Infiltration", she was shown to enjoy dancing as she is seen dancing by herself between two Atlas Soldiers. Later that night, she's seen doing "the robot" with one of the soldiers.

Penny's most notable trait was her kindness. She greeted the recently met Team RWBY with a jovial "Salutations!", complimented Weiss' hair, and offered to help Ruby track down Blake. In addition, she saved Ruby from a truck before asking the driver if he was okay, thanked Team CRDL during the Vytal Festival for the time she had, and told Pyrrha Nikos in the finals that it was a pleasure to finally meet her.

Penny's stranger social quirks tone down as the series progresses. While her early appearances had her depicted as cheery, curious, and unfamiliar with most aspects of social interaction, these aspects appear to diminish with each subsequent appearance, and by the time of the Vytal Festival, Penny was barely distinguishable from her former self's naivete and volatile emotional state, sharing a conversation with Ruby about her plans to stay at Beacon and her teammate.

[This is what she sounds like...]
https://www.youtube.com/watch?v=hxZnResFLxo