This concept struck me because last week I decided to push myself through completing the Half-Life series. While playing Half-Life 2 and the episodes, I noticed that one prominent female character, Alyx Vance, was continually making comments about how great the protagonist, Gordon Freeman, is. For context, Gordon is a theoretical physicist who graduated from MIT. During the first Half-Life game, Gordon fights aliens that have infiltrated Earth. In the second game, Gordon is renowned for doing so, and as soon as you meet Alyx, she begins telling you how excited she is to work with you.
It was at this moment that I realized that Alyx really has no character. She's not really in the game because she has her own motivation or arc, she's there solely for the player's existence, to tell them how cool they are, how smart they are, and to be saved. Heck, even in the game's poster, Gordon is depicted as being in control and having power, while Alyx looks afraid and out of control.
In the episodes (the short games following 2), Alyx becomes even worse. Even after doing simple tasks, like killing the same large monster for the seventh time, Alyx will tell Gordon how magnificent he is for doing these simple tasks. Other characters will also make suggestive comments, that Gordon's progress will ultimately result in some sort of romantic relationship with her. Alyx's father even suggests that Gordon is prime candidate to help her "repopulate Earth."
These kinds of things are troubling (and they relate to Sarkeesians analysis) because a lot of women in video games, like Alyx, are not really characters. They are traveling voice boxes meant to either titillate or promote the skill of the presumed straight male gamer.