This is actually not Snoopy's first instance talking! The first was another strip, coincidentally also a one involving costumes, in which he, covered with a sheet, says "Boo!" That's some vocabulary that dog has.
This is a pretty silly strip, but I like it. The fancy shadow on the first "Boo" is probably a first for the strip.
By the way, we can tell it's Violet beneath the sheet through simple process of elimination. There are only five human characters right now, and Schroeder's still too short to be confused with the other characters.
