I have a question! When did Deadpool learn he was a fictional character?
Wade first figured out how to break the fourth wall (thus leading him to the full understanding that he is a fictional character) back when he had a succession of encounters with Loki (also back when Loki claimed to be Wade’s father! Craziness!). Loki, being the snarky god he is, told Deadpool the ‘secret of the universe’ and told him that “there was a man with a typewriter.”
This happened around or in (and if I am wrong PLEASE correct me!) Deadpool #37 during the Priest run.