For the Mimiron encounter in Ulduar, you fight several of his creations: Leviathan MK II, VX-001, Aerial Command Unit, V0-L7R-0N. This was considered to be one of the most difficult encounters in Ulduar, yet also the most fun to start—you pressed a big red button.
Mimiron yells: It would appear that I've made a slight miscalculation. I allowed my mind to be corrupted by the fiend in the prison, overriding my primary directive. All systems seem to be functional now. Clear.
Mimiron yells: Now, why would you go and do something like that? Didn't you see the sign that said, "DO NOT PUSH THIS BUTTON!"? How will we finish testing with the self-destruct mechanism active?