The term "Black Friday" refers to the first shopping day after Thanksgiving in the United States. Many people believe that the "black" part refers to retailers who are swamped with shoppers and are therefore at last "in the black" (a holdover phrase from the accounting practice of using black ink for profits and red ink for losses). But those people are wrong! The term originated in Philadelphia in the '60s, and "black" actually had a negative meaning: increased traffic on the streets meant more accidents and fatalities, so the police are the ones that began calling it Black Friday. Retailers didn't like the idea of it having deathly associations, so in the '80s they set about reclaiming it and spreading the version you probably think of today.
The Black Lanterns - Hawkman, Nekron, Wonder Woman and Batman - come from DC's Blackest Night crossover, in which the dead rose to walk the earth. The shopper is Robot Chicken's Nerd; try reading his lines in the voice from the cartoon!
Oh, and if you wonder what Batman is talking about, he's trying to recruit the Nerd to be his next doomed sidekick. For his exclamation of "hooperball," check out this toon from the beginning of the month.