Messing around with the past can have disastrous results, though Lea Thompson was almost hot enough to warrant negating your own existence by doing your mom. For past-twisting prints that don't end horribly, check out Alternate Histories.
The work of a former filmmaker with mad Photoshop skills, AH takes authentic old lithographs, etchings, and other historical documents and digitally alters them with hilarious incongruities like robots and monsters, which blend in so seamlessly they appear normal at first glance, kind of like married guys who like getting groin-stomped by high heels, but not as terrifying. Some standouts:
Chicago In 1820: A rendering of the Windy City's early days as "an untamed prehistoric wilderness" depicts the verdant landscape crawling with dinosaurs, which became fantasy once they all figured out they could relocate to Florida.
The Menacing of the East River Bridge: A work celebrating the opening of what NYC now knows as the Brooklyn Bridge gets an unwelcome visit from a tentacled monster, though once the local denizens fought back it turned out to be a total octo-pussy.
The Signing of the Declaration of Independence: John Trumbull's iconic rendering of America's baby steps finds Founding Fathers like Jefferson and Hancock joined by humanoid robot Metallo the Mechanical Man, whose being from the future was almost enough to stop Ben Franklin from doing him.