There are many conventions or conventional aspects to the "Zebra Storyteller" by Spenser Holst. Since the story begins with the fairy-tale opening of "Once upon a time..., this seemingly innocuous and conventional opening sets up what may either be a conventional or scripted fable in which the events will be foreshadowed, known, and readily understood, or the opening can lead into a false sense of relaxed understanding to a known convention of the fable or fairy tale. The one-sentence moral at the end of the story belies a greater strength to the story in which readers may not have completely understood what they have read.
The types of narratives that conventions play in st0ries like this adds a greater resonance to their expected structure. The phrase "Here now" at the beginning of the third paragraph adds to the deepness in which the story not only has some verisimilitude years ago (One upon a time) but has sustained its verisimilitude by having current value (Here now) as well. It might be used inappropriately, but there might also be a hidden truth to the message of that statement. The cliche "fit to be tied" is used in reaction of the zebra to the cat. This conventional language can be seen as having greater impact in light of the action of the story.
It appears from the opening line of the story that the storyteller will prepare us for something unexpected as our guard is down in expecting a standard fable or fairy tale. Clearly the storyteller has insight into the ways a story should be told and the story also emphasizes the the power of imagination. Like the cat imagining that it is a lion to accomplish great things, places the story in a greater context of the storyteller, and the imagination that it requires to listen carefully to a story and to be informed, entertained, and educated, all at the same time.