Marvel's Deadpool is known for his over-the-top violence and crude and crass humor, but perhaps his best-known character trait is his penchant for repeatedly breaking the fourth wall. Deadpool talks to the audience in comics, films and videogames - but he didn't always have this power. In fact, early Deadpool was known for being quite serious and firmly rooted in the fictional realm...so when did the Merc with a Mouth first break the fourth wall - and how did he insult editors everywhere by doing so?
First appearing in The New Mutants #98, Wade Wilson - a creation of artist Rob Liefeld and writer Fabian Nicieza - stuck out due to his striking yet simple design. He didn't have the giant shoulder pads, open cowls or long, flowing hair shared by other edgy and extreme 90s heroes, but he did have twin swords and an intimidating visage. Over time, his humor became more and more prominent (and increasingly irreverent), but it wasn't until Deadpool #28 by Joe Kelly and Pete Woods when Deadpool finally began his long tradition of smashing through fourth walls - and it began with a bang.
Deadpool and the assassin with superhuman accuracy Bullseye teamed up in previous issues, and in Deadpool #28, the two are reunited after a long absence. "How long has it been!?" Bullseye exclaims. Deadpool simply states "Issue sixteen." It's the smallest of fourth-wall breaks (he hadn't even began speaking to the readers yet), but it shows that Deadpool is doing more than acting out - he's acting as his own editor. Considering convoluted comics continuity, it's normal for editors to occasionally place footnotes in certain panels, specifically when characters reference past events. Perhaps Kelly and Woods considered the old method, but wanted to try a new technique. Whatever their reasoning, Deadpool's fourth wall breaks became a staple of the character.
Deadpool would continue making sly winks at the audience and referencing issue numbers, but the ultimate fourth wall break wouldn't arrive until Deadpool #33, when a scientist captures Deadpool and subjects him to numerous tortures. Wade takes absolutely none of it seriously and finally reveals the reason why: "None of this is actually happening. There is a man. At a typewriter. This is all his twisted imagination." The scientist, naturally, doesn't believe him - and neither will anyone else, for every time Deadpool breaks the fourth wall in comics, all the other characters around him (and even his friends) simply think he's crazy.
This is the underlying tragic nature of Deadpool, and his unique knowledge of the fourth wall and the universe beyond. Imagine knowing a fundamental truth about the world that can never be understood by - or explained to - anyone else. In this respect, Deadpool is utterly alone within the Marvel Universe. But seeing as he knows he's a fictional character, it's entirely possible he just doesn't care.