I'm not sure. Maybe it's just some random creative thing.
The political cartoon might focus on highlighting the controversial aspects of the Pentagon Papers, like government secrecy or policy decisions.
The cartoon baby could be smiling because they just got a hug from a loved one or had a delicious treat. Sometimes, babies smile for no obvious reason, just because they're in a good mood!
It could be that the cartoon kid is smiling because they just accomplished something they were working hard on. Or perhaps they're in a beautiful and fun place that makes them happy.
The cartoon horse might be smiling because it accomplished a goal or is surrounded by beautiful scenery that makes it feel cheerful.
Maybe it's having a great day and something made it happy.
Maybe he's just having a great day and something wonderful happened to him.
Maybe it's in a good mood or just having a fun moment.
Perhaps he's smiling because of a kind gesture or a positive interaction that has touched his heart and made him show a different side. After all, everyone can have a turn for the better.
It could be that she saw something funny or received a wonderful surprise. That's why she's smiling in the cartoon.
Maybe she's having a great day and something wonderful happened to her.