Oh god - this is one of my favorite "time waster" games...
Historically I've had the "can't picture anyone else" problem with Michael - EVERY scene I imagine an appropriately aged Liam Neeson.
For Murphy I like Kristen Bell. This just works:
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I like Charlize Theron for Mab.
For Marcone I like Ray Stevenson:
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My sadness here is that I just don't have a Harry. No one has ever seemed "perfect" to me.