A familiar character enters the episode with a lizard-like appearance:

She introduces herself to Marge as if they barely know each other, which is interesting, as Helen may be Lisa's godmother (this is revealed in "Treehouse of Horror XX" so may not be canon.)
In this initial scene she identifies herself as "the gossip wife of the minister", which is a perfect encapsulation of her character. This line is basically intended as a joke, in that this cartoonish stereotype would literally be the least convenient person for Marge to bump into while out with a man that is not her husband, and as such it's surprising that Helen became a regular familiar cast member. But the writers take this fairly simple characterisation and run with it.
Helen is on the surface a flimsy character, used mainly as an outlet for the show's attitudes towards sheltered middle-class America, how she appears to feel superior towards those around her and often feigns concern for the sake of appearing virtuous. Her 'catchphrase' "Won't somebody please think of the children?" is indicative of this - she doesn't really care about 'the children', she just wants people to think she does.
This type of personality should perhaps lead one to the conclusion that she would be an unpopular or disliked character - I wasn't a huge fan of her when I was younger, seeing her as a barrier to fun. But despite this, I encountered a simple recurring theme in researching her:
The internet is horny for Helen Lovejoy.
This is not universally true. But more than any other character, when looking for information about her, I found raunchy fanart of her in various outfits. This is a family blog (I guess?) so I will leave you to reach your own conclusions about why people might be especially attracted to a stuck up middle-aged housewife with a holier-than-thou attitude. I just thought it was interesting.
This post is part of my "Every Simpsons Character Ever" series. For a list of my rules in this project, click here.