Hehe. Don’t doubt the stupidity of some folk. The Darwin Awards were invented for a reason. 
Thats why im going to start with the back wheel of a bike. That should be fairly safe cause its so far from your legs.
Then if that works out I’ll try it on my more precious unicycles.
Sounds like a good idea… Be sure to have a few buckets of water on hand. 
Safety first, kids.
It movies they use a special gel that you can set alight and not feel a thing. I think its called “Fire Gel” search for it on youtube and watch some videos.
I’ve done quite a lot of playing with fire and am not dead or even mildly singed yet. A few safety rules:
First things first, make sure you have a bucket of water and preferably a fire blanket handy. If you do get your legs on fire, ditch the unicycle, and get onto the ground and roll over till it is out / whack it out.
Make sure you are wearing clothes made from 100% natural fibres, I usually wear heavy cotton jeans for when fire is going anywhere near my legs, and long sleeved cotton shirts for anywhere near my upper body. Whatever you do, don’t wear anything with polyester or nylon in - they will melt onto your skin if they go near fire.
Make sure that wherever you are doing the fire, you aren’t near anything that will burn easily - ie. not on dry grass, not near cars etc. If you’re using any long burning form of fire (using kevlar etc.), don’t do it anywhere where you’re going to be stopped by security / police etc. - as security guards tend to get annoyed with the person who is playing with something on fire, and won’t stop it - they don’t know that you have to keep it going until it goes out or risk damaging your equipment.
Have a plan to put out the fire in the case of hassle / someone burning / you falling off, and make sure someone who isn’t on the unicycle knows what to do if your trousers start burning. If you fall off, you’ve got to get the unicycle either moving again quickly, or extinguish it, or you risk damaging the unicycle.
So that’s the what not to do. Onto what to do:
There are 3 ways I’ve seen to set a unicycle alight without burning yourself to death.
1: lighter fluid onto the tyre, light that, ride away fast.
2: Kevlar rope soaked in paraffin through the spokes, light that, ride away and don’t stop until it burns out.
3: Juggling fire clubs attached to pedals. I actually have a special set I made simply out of copper pipe with kevlar attached to the end, cost about £4 for the kevlar, picked up the copper pipe for next to nothing. You strap em onto the pedals using any old strap and a lot of gaffa tape.
The advantage of lighter fluid, is that it’s a very short burn (like 20 seconds), so no major worries as long as you keep riding. I’d guess you can also do fire circles with it - where you put circles of something that will set fire on the ground and ride through it to set it alight. Fire circles are quite dangerous and naughty though, so only do them if you’re really certain about your safety, and you don’t mind leaving a bit of a mess (somewhere like an empty carpark or something is good for this).
The advantage of the rope, is that it burns for a good while. The disadvantage is that it burns for a good while. You really need to keep the unicycle moving all this time, or else you will burn up your unicycle / your legs. The only sensible way to put it out is with a lot of water, or dunking the unicycle in water.
The fire clubs/copper pipe version is really cool, quite long burning and not as dangerous as rope - but you do get flames licking up your legs a bit. I’ve done it in shorts, but I’d usually choose to wear heavy trousers that are quite fireproof. It looks really cool - kind of like a flaming chariot effect, although maybe not quite as good as the tyre one. You have to be careful in dismounts not to damage the clubs. It can also be applied to pogo sticks, which look really great with the flames shooting up when you bounce. It does no damage to your unicycle either, and if you have a bucket of water, you can extinguish in it just like normal fire clubs.
Also, about the person who mentioned fire safe gel - I’ve talked to people who know about it, and places that make it will usually not sell you it without you having safety certification and training in using it. This is for good reason. If you don’t know how to use it, you can get yourself burnt really badly. Even proper stunt men get burnt when they mess up fire stunts. If you’re planning something that needs it, you’re probably planning something too dangerous to be sensible to do just for fun.
Joe
Yeah, it looks great. But it isn’t as simple as you say that you “don’t feel a thing” - look at the fire extinguishers at the edge of the screen in that video, and the way they hose people down with them afterwards. You inevitably get pretty hot after a bit, and you need to cool it off very quickly or else you can get really badly burnt. If you read the safety info on this stuff, it is very scary. I did a bit of research on this in the past, and there is no way I’d go near it.
Apparently, playing with fire with stunt gel, you can get hurt worse than without if you don’t know what you’re doing - as you get a burn that goes too hot and you don’t extinguish it early enough, then you’ve got hot sticky goo all over you, rather than just being able to put out a fire on your clothes.
Joe
I did that on Halloween:)
Playing with fire is fun… and it definitely can be stupid, but that mostly depends on the stupidity of the person playing with it.