Some people like to pack elaborate camping gear when they go motorcycle camping. You don't always need the latest fancy schmancy gadgetry, though. Let's say that after a long day on the road, you want to relax with a bowl of popcorn. Forget the camp stove, frying pan, and oil. True or False Experiments shows us that your muffler, already warmed up from the ride, will take care of everything for you.
Getting Back To Nature
Okay, my tongue is extra firmly implanted in my cheek as I make that recommendation. Please don't do this, except maybe if you're about to replace your exhaust anyway. Fortunately, these guys already tested it for you and determined that you can, in fact, pop popcorn inside a hot motorcycle exhaust.
Their first attempt involves making popcorn while the Yamaha R1's engine is running. This works but proves problematic because of the air rushing through the exhaust. Any application of throttle causes the popcorn, both popped and unpopped, to come flying out the back of the bike. This provides little control over the popping process, not to mention the collection of the popcorn for ingestion purposes.
The next try, pouring popcorn into the hot muffler with the engine off, proves much more successful. You can actually hear the popping going on inside the muffler due to the ambient heat. Of course, extraction of the popped corn is still an issue, so the easy solution is to fire up the engine and blast it out with the throttle. Perhaps a strainer would work well to collect it without impeding the exhaust airflow.
There are other issues as well. You don't want to be eating popcorn tainted by unburnt fuel, oil, or anything else that's been inside your engine. So really, don't ever do this, unless it's for a laugh instead of a snack. Perhaps you could test whether loud pipes make a difference in how well it pops.