Andersen's tone varies a lot, from wry ("Little Claus and Big Claus") to earnest ("The Pact of Friendship") to sentimental ("Little Ida's Flowers") to condescending ("The Emperor's New Clothes").
It's hard to miss some of Andersen's more extreme tonal play. In "The Emperor's New Clothes," Andersen describes the scene in which the emperor puts on his fake clothing for the first time: "The emperor stood in front of the mirror admiring the clothes he couldn't see." (9.31) Yeah, the tone is pretty critical there, since it's obvious to us readers that the emperor is an idiot. Put some clothes on already, will ya?
A lot of tales fit the "sentimental" bill. In "Under the Willow Tree," the main character's family receives a letter from some family friends, and, upon reading the happy news in the letter, "They all wept" (67.18). Um, seriously? We know that's supposed to be sweet, but earnestness is, like, so 19th century. And if that's not enough, in "Little Ida's Flowers," we see Ida's flowers come to life at night and throw a party. Then they say to Ida's doll: "It is most kind of you, but our life is short. Tomorrow we shall be dead. Tell little Ida to bury us out in the garden where the canary is buried; and next year we shall come back to life again and be even more beautiful than we are now" (4.51). Yeah, that was sappy enough to make us want to swig some mouthwash.