I had a Peacebringer "Novaspark". Her background story was that she was a 14yo, and a bit small for her age, sent back from the future.
If in human form she would get too much agro she would shout "Hey! Pick on someone your own size!", then morph into Dwarf form and do her best Hulk smash impressions.
It was always fun to see team members (especially new players) back off in awe as she would rampage through mobs clearing entire rooms all alone.
Usually after a couple of minutes and clearing several rooms her rampage was over and she would turn to her team members, morph back into human form and say something like "Okay, I'm done now." or "Sorry you had to see that.".