There are two more "penis" moments in Baby Mama that stuck in my mind:
One, when Tina Fey's character is with her new boyfriend, the fruitshake-making guy, and he points out the graphic of a banana in the window of the shop and asks her if it looks like a penis. Stupid scene in my opinion--unnecessary and sophmoric. Again, it's what Peter Lehman is talking about...
Two, when Tina Fey's character orders a meal from a takeout stand and makes a lot of requests for how she would like her food done. She apologizes to the new boyfriend for being so demanding and controlling and he says, "That's not fair, if you were a man, people would call you a 'dick.' And Fey says something to the effect of, "Aww, no one has ever called me a 'dick' before."
This second joke was commenting on something interesting in society--how if women act too strong they are called names, but this is seen as a strength in men.
But the larger point is that author Peter Lehman is right, "there has been an increased emphasis and centrality on the penis in our culture," e.g. all these increased references, visually and verbal, to penises in recent movies.
As Lehman says, he and his co-author Susan Hunt think this is part of an increase in emphasis on the "body" in our culture, i.e. dieting, physical fitness, an obsession with youthfulness, "an intensification of a particular body culture which devalues the mind, and overvalues the body."