Why is "Mister Death" given that name? What does that have to do with Buffalo Bill?
"Mister Death" is Cummings's trademark whimsical way of addressing death itself. In the context of the poem, it is a direct address; with traditional punctuation, the last two lines of the poem would read something like, "How do you like your blue-eyed boy, Mister Death?" Cummings makes a shift in whom he is talking to in these last two lines; whereas he is speaking to the reader in a general way in the majority of the poem, in the last two lines he is speaking directly to death. The blue-eyed boy, of course, is Buffalo Bill, whom Cummings has just described as being "defunct". Cummings's point is that even though Buffalo Bill Cody was an amazing man, larger than life, who could perform amazing feats, still, in the end, death took him just as death takes everyone else.