U.S. actor Will Smith (R) and South African actress Charlize Theron arrive for the opening of the Moscow Film festival where they are promoting their movie 'Hancock' in Moscow June 19, 2008.[Agencies]

A Will Smith movie packs in millions of people over Fourth of July weekend. No surprises there.

Yet Smith's "Hancock," the tale of an anti-social boozer who happens to be a superhero, comes with an abrupt plot twist, one that has divided critics and the moviegoing public in the real world (Critics and everyone else can't agree. Now there's a real surprise).

For those who have yet to see "Hancock," we won't give the secret away, but it has something to do with why Charlize Theron's soccer-mom-style character doesn't want Smith's surly superhero anywhere near her family.

Critics generally thought the turn the movie takes halfway through was a cheat, spoiling what had been a promising idea that was a fresh twist on the superhero genre in its own right.

The people who turned "Hancock" into an instant blockbuster beg to differ — to the sum of $185 million worldwide at the box office in just a few days.

The plot twist in "Hancock" won't go down in cinema history alongside Darth Vader revealing he's Luke Skywalker's pappy in "The Empire Strikes Back" or Anthony Perkins turning out to be a slasher in his mom's housedress in "Psycho."