Dragons need fire, right? To tell the truth, making fire would be quite easy to do, but I think it would be (strongly) discouraged by Con officials...
So the trick is to make something look like it. Smoke machines (quite a few sources on the 'net about these) use a glycerin/water mixture sprayed on a heater, and Errol uses the same idea... only smaller. An old microwave (food-ready sensor) provided the heater, but these can come from CO/gas detectors or E-cigarettes. Rather than spray the fluid, Errol uses an oil-lamp wick through the heater and a sealed reservoir (filled from a tube under the nose) for the fluid. A small fan directs the smoke out the nose. Small LED lights that flash give an 'inner-fire' effect.
To make Errol let off smoke, the tiny sensor from an E-cigarette is mounted near the base of the tongue- blow on it and a signal to the computer begins a timer for a relay that runs the heater. (these sensors also have a tiny light. Will run from 5 volts and provide a pull-down signal when blown on from the back side) About 1 ampere of current flows at 6 volts for the unit I did. The heater would get red hot, but the fluid cools it. The whole thing is mounted in a small box made of double-sided PC board material soldered together.
I have had zero success trying to make one of those fabric flames work... anyone try this?