So I went ahead and tried my luck, here is my research based on my experience...
When you "use" a Stuffed Dragon you have the chance to get various messages with different occurences:
As we know, the Extremely Rare Message "You... will.... burn!!" will also "burn" you and you'll recieve fire damage for 1 hitpoint... but, what is the chance of this happening?
Stuffed Dragon 2,000 trials:
In my case, I got the "You...will...burn!!" message in the attemp # 1889 out of 2000 trials.
For the additional question whether is there any screenshot on the web confirming the "You...will...burn!!" sound, you can find the uncropped version here: TibiaGallery Stuffed Dragon.
Additional notes:
- I used only 1 Stuffed dragon during the whole research
- The Stuffed Dragon was not in my backpack, it was on the floor, therefore all the clicks were done "manually", no hotkey used
- I was wearing Fabulous Legs and Falcon Escutcheon (yeah, silly me) so I was not hurt for the 1 hp since the damage is fire based
- I wasn't on PZ during my research. I was on Darashia Desert
- I do not have the "I need hug" Achievement