"common knowledge", really ?
you are just another rat consumed by his inferiority complex.
He is a rat, but he is partially right,
Sriman Bhagavatam gives a physical description of Krishna,
Barhapidam nata-vara-vapuh karnayoh karnikaram
bibhrad vasah kanaka-kapisam vaijayantim ca malam
Translation is,
Wearing a peacock-feather ornament upon His head, blue karnikara flowers on His ears,
a yellow garment as brilliant as gold, wearing a necklace of Vaijayanti beads,
His name "Krsna" means Black/Dark.
It further says,
randhran venor adhara-sudhayapurayan gopa-vrndair
vrndaranyam sva-pada ramanam pravisad gita-kirtih
Translates as,
His enters gracefully like a master dancer into the vrindavan forest,
and plays the flute while the cowherd boys sing his praise.
So, by this we get that Krishna was talk dark handsome attractive man who walked gracefully, dressed in bright Yellow, a white bead necklace on his neck and a Peacock feather Crown/ornament on his head.
Amir Khan is neither tall, dark nor graceful. I do not think he will fit that role, though I am sure he can act the role. But any Hindu seeing him will not see "krsna" the dark one.