When my pet tank and I encountered our first tyrannosaur in the jungle, we initially weren't sure whether we were meant to fight or flee. It hardly seemed to take any damage at first - until we knocked it over, which seemed to temporarily apply a massive damage buff.
"It's Kephess!" I exclaimed.
That probably won't make sense to 99% of my readers, but I wanted to write it down for future reference anyway.
(Boring explanation for anyone who really wants one: In SWTOR there is a reptilian (Trandoshan) raid boss called Kephess, who got revived repeatedly after being beaten several times. Thanks to this, it became a running joke that he's everywhere, secretly responsible for everything etc. In his second incarnation, one of the fight's major mechanics is to knock him down to do increased damage to him. The similarity just struck me as quite amusing.)