Was just messing around on the Mount Doom map when I decided to sick my Mumakill on a wild fire Drake. Killed it but my elephant had less than 25% of it's HP remaining. The fire animation stayed even after it stopped doing damage. So now my Mumakill and Haradrim archers are a walking inferno. They were strangely indifferent to it.
P.S. I did try to put it out with my builder's bucket of water but it didn't work.
Looks more scary when it's burning.