First, the 1931 production of Frankenstein is the most famous film version of this classic scifi tale. Hancock's only evidence of his past life is that he was holding two ticket stubs from that movie, which he was seeing on a date with Mary when he was mugged. (It's weird thinking about what word to use for the men who attacked Hancock, since so many of those words - thug, goon, asshole - you immediately think of how they were used on Hancock himself.)
Whenever a film contains diagetic art (especially another film) this is usually a blatant cheat sheet for what themes the movie is exploring, since few directors can resist fitting in a cute allusion like that. Notice how at the beginning of Sneakers, the security guard is watching the Maltese Falcon. My favorite is probably during I Am Legend, there's a scene with Shrek playing in the background, where the cartoon animals perfectly encapsulate the tense argument not-being-had by the real characters. (Go see I Am Legend. It's so good. Make sure to choose the alternate cut.)
So yeah, the Frankenstein tickets are Berg yelling "This movie is about a scarily powerful man who wants to help but is alienated by the villagers!"
The 1930's also gave us Superman. And Hancock is pithily described as "What if Superman were black?" He wouldn't be raised by a nice couple on a farm and revered by the world - he'd be homeless and reviled by classes afraid of his power.
(This may seem a trivial coincidence, but it means that Hancock in his current iteration has basically existed for as long as the superhero myth in American culture.)
And then there's racism. (Which no, this blog will not be including an iconic picture of.) The 1930's were in some ways the height of cultural racism - it's not legally ordained like slavery, but legal equality isn't codified the way it would be after the 1960's, and the depths of the Depression render the class conflict inherent to racist ideology unto its nadir.
To briefly steal a quote from SMG again (about the movie Zootopia):
I wrote that racism is a mask for class conflict. Racism is an ideology that, for example, justifies the exploitation of black people by rendering it 'natural'.
Remember: race is a social construct invented as justification for the slave trade, only a few hundred years ago.(The terms 'racism' and 'classism' were coined within 60 years of eachother, shortly after the industrial revolution and during the advent of industrial capitalism. 'Racism' is a derivation of the word 'classism'. Both words are less than 200 years old.)
One function of racist ideology is to prevent solidarity between blacks and poor whites, just as sexism is deployed to prevent solidarity between poor men and women. Antiracism is not 'unimportant' to Marxists. Antiracism is a vital part of the broader - universal - emancipatory struggle.
Just as Ray is trying to participate in a universal emancipatory struggle (symbolized by his cartoon heart on the frickin moon) by helping one black man in particular recover from the social effects of racism.
What's particularly great about using this time frame and reference set, is that it leads to this exchange at the fancy restaurant dinner:
RAY: What about you buddy? You’re from another planet, aren’t you?
HANCOCK: Naw man, I’m from Miami.
RAY: You didn’t come in on like a meteor or …?
HANCOCK: Nope, woke up in a hospital, first thing I remember.
RAY: Government hospital, yes? Experimenting on you and...
HANCOCK: No Ray, regular ole Miami emergency room.
RAY: Come on?
HANCOCK: Yeah my skull was fractured. They told me I tried to stop a mugging...
RAY: Somebody knocked you out?
HANCOCK: I guess I was a regular guy before and when I woke up I was changed. The hospital nurse tried to put a needle in my arm and it just broke against my skin and then my skull healed in like an hour.Doctors were astounded and umm they wanted to know my story. Just like you but, I couldn’t tell them. I don’t know who I am.
RAY: Amnesia. You know the blow to the head.
HANCOCK: Yeah well that’s what they figured.
RAY: You don’t remember anything?
HANCOCK: The only thing I had in my pocket was bubble gum and 2 movie tickets Boris Karloff, Frankenstein. But no ID, nothing.I went to sign out and the nurse asked me for my John Hancock. So I actually thought that’s who I was. 
RAY: How come I didn’t hear any of this, read about it in any newspapers?
HANCOCK: It was probably in the papers... about 80 years ago.
RAY: 80 years ago.
HANCOCK: Oh.. I don’t, I don’t age.. This is it.
(Apologies if I keep spoiling the best bits of the movie for you. Your only option is to watch it yourself and find meaningful readings of other good bits of dialogue for yourself.)
What's going on here is fascinating. Ray is searching for the deep, obscurantist secret that explains Hancock. In comic book logic, he must be some alien, or covered up by a government, and we can only learn his origin by exploring mysteries that must be hidden by others. Ray is acting as a conspiracy theorist, who explains difficult realities in terms of the fantastic. He's like someone who thinks black people in America are held back because the government is putting something in their water supply. And because his explanations strike us as common-sense-for-the-genre, we are put in that perspective as well.
And Hancock responds, no, all of this was out in the open. Major newspapers reported on Hancock's hospitalization, just as they reported on the conditions black people were subjected to 80 years ago. And time went on and it was no longer new and people stopped caring. We are so much worse at responding to old injustice, than we are at new and interesting intrusions.
The film explained that in 20 seconds of moving dialogue, much better than my two paragraphs of analysis. Which is what makes it great.
 Only on this re-watching did I notice the value of Hancock's name. His very name is a universalizing factor, a symbol that stands in for anonymous identification. Hancock could be anyone.