Tom Hiddleston/Sherlock, Benedict Cumberbatch/Loki. This would be fascinating! - that's putting it mildly! <--This is terrifying..... <--- Is it terrifying? IS IT?! No, this is a role switch, we can giggle. <-- Heh, nice reference.
The great thing about this pic is it totally shows what everyone likes to point out. Ben creates a character completely separate from himself. The only connecting factor is he is the actor playing the character. And it is times like this pic that show it. You never see sherlock with this look on his face. This is a moment if Ben shining out from behind the costume and being himself.