The icicle-dripping word balloon in the second panel is nice.
Let's talk for a moment about the Peanuts characters' repertoire of expressions.
1. Neutral: No mouth at all when viewed in profile, a small dot or dash when viewed from the front
2. Mild Surprise/Interest: Neutral, but with small, upside-down-U eyebrows over the eyes. See Violet in panel four here.
3. Happy: Triangular mouth in profile, standard smile from the front or a faked profile triangle.
4. Angry: Eyebrows drawn as one long line from the front ("unibrow"), diagonal eyebrows going down towards nose when viewed in profile. Mouth is Neutral if mild anger, or a horizontal line if stronger.
5. Worried: Similar to Angry, but with slanted eyebrows arcing up at the nose line. Also, no unibrow. Mouth as in Neutral. Charlie Brown in all frames here, also Violet in panel three.