This is the first time the word "fussbudget" has been used in the strip. Now this word is almost impossible to separate from Peanuts. It is always, or nearly always at least, connected with Lucy.
Lucy hasn't been extremely fussy up to this point, but in Peanuts, when another character makes explicit reference to some trait supposedly possessed by another character, that tends to be the point where that other character begins exhibiting that trait as a defining characteristic. In other words, when someone is labeled, the label becomes indelibly part of them.
This is how most Peanuts characters evolved over time, and especially how they gained the traits for which they became memorable.
