Harry must never inform any of his enemies of the existence of the Evil Overlord's List

Nor may he ever ask to hear Cowl's rendition of "Slaughter Your World"
(Looking For Group Reference)

Nor may he ever break into montage related theme song while Molly is training, not even Eye of the Tiger.
He may however make use of other Rocky references including but not limited to:
"I didn't hear no bell" "I will break you" "Get up ya Bum!"
Note: "ADDRIANNNNNNN!" is strictly forbidden.