They are purple rhynocs in green kimonos. They will light fireworks and fire them in Spyro's direction in an attempt to harm him. They can be defeated with a ram or a flame; however, the flame will ignite their fireworks and send them spiralling into the sky before exploding.
It is also possible that they can kill other enemies with their rockets accidentally. For example, if Spyro stands between a Fireworks Rhynoc and a Rhynoc holding an umbrella, and if he jumps out the rockets, the rocket will shoot the Umbrella Rhynoc and it defeats him. Some players found it also works with the Egg thief, too.