I really love this poster. It is, to some extent, just a head shot. But when coupled with the tagline, it’s the perfect image for this movie, telling you exactly what the film is about and why you might want to see it.
No, of course you wouldn’t want to have a baby with this guy, he looks completely unprepared to be a father. On the other hand, watching him trying to deal with his upcoming fatherhood might be very funny. And Seth Rogen is likable enough, so we also want to see him succeed, even if it takes some growing up.
The other posters are also nice. The second one does a good job of setting up the relationship aspect of the movie, showing that these two aren’t exactly madly in love with each other. The third one is mostly a visual pun, but it’s a decent one, and it makes for an attractive and catchy image.
But that first poster, that one would probably get me to see this movie even if a didn’t know anything else about it.