Transcript for 'Girls' Episode Sparks National Discussion on Beauty
We're going to do a story, now, about something that's called dating up or dating out of your league. It was something that came up very recently on an episode of "girls." Lena dunham's character, very celebratory of her disheveled look, dating a very good-looking guy. And a lot of people got worked up about this whether it's a real issue. And it actually is. Abc's juju chang has the story. Reporter: She's hollywood's unlikely it girl. Yet, mismatched clothes and all, some saline in a dunham has captured the voice of the 20-something generation, playing hannah, in the award-winning hbo show, "girls." Which she writes and directs. On a show already known for pushing boundaries -- unlike you, I'll do almost anything sexually. Reporter: But what she did stirred controversy, when an unkemped hannah, has a multiday affair with joshua, an older, wealthy, handsome doctor. You are very beautiful. Reporter: But this morning, these mismatched mates on tv, have opened up a real-life debate online. With critics saying, he's out of her league. And calling the tryst between such different-looking and acting characters, implausible. Even uncomfortable. While others say, it was charming, even evocative. Why are people up in arms? It's unkind. Bup it's human nate. Reporter: Social psychologists have long-documented our human tendency to pair off with like attractiveness. When a supermodel is paired with a less-than-supermodel, it sends shock waves. And folks assume the mismatch is made up by money, power or social status. It's not just physical. Their need is being filled by this person. Our thanks to juju chang. I did a story on this for "20/20" with real couples who are married. And people come up to them on the street and comment on the asymmetry of the relationship. Causing a debate.
This transcript has been automatically generated and may not be 100% accurate.