Read this comic at gocomics.com.
In this strip, we begin to see that Schulz is becoming more careful about showing emotions. It's not just the hilariously shaken image of Linus in the last panel, it's that we can't get a good read on why Lucy did this. She betrays no satisfaction or joy throughout the process. It's like she's just doing what her mother told her like a good little girl. But why is she sneaking up on her blissful brother? Why is she shouting at him? Later on the thrust of whole strips turn on whether a character's mouth was drawn with a slightly upturned stroke.
This is the third strip to use the "somersault" visual shorthand for violent disruptive motion. The first time was in the first football strip (which has still yet to become a yearly thing). The second time was, interestingly, another instance involving Lucy shouting near Linus.
