Spike is Twilight very helpful and number 1 assistant. At the start of the story anyway. After a certain event across the ocean, spike gets along much better with Navarone and starts to age at a faster rate and becomes more like a teenager. Spike starts off as the spike we all know, but he will get bigger and bigger as the story goes along so just be sure that you can go from a child voice to more of a teenage voice with this character.