Seven years before Deadpool proved one of the most surprising superhero movie successes ever, Ryan Reynolds played Wade Wilson in X-Men Origins: Wolverine, a movie that was considerably less beloved. After years of trying to convince 20th Century Fox to bring the character to the big screen, he finally got his wish, but his duties extended beyond just the acting work. Off-camera, he also wrote Wade Wilson's lines. According to Reynolds:
It was during a writers' strike, so all my dialogue in X-Men Origins: Wolverine I wrote. I mean, in the stage directions it just said, "Deadpool shows up, talks really fast, and makes a lot of jokes." At the beginning of that movie, that's pretty close to Deadpool's Wade Wilson---we're in the ballpark with that guy.
During a lengthy GQ interview, Ryan Reynolds explained how in addition to playing Wade Wilson in X-Men Origins: Wolverine, he also wrote the character's dialogue because of interference from the 2007-2008 Writers Strike. This version of Wade Wilson popped up at the beginning of the movie as one of the the members of William Stryker's mutant strike team, and true to form, he was quite the wisecracker, much to the annoyance of his fellow operatives. It was the closest the movie came to giving fans a proper Deadpool, and given Reynolds' penchant for comedy, it's fitting that he was the one who penned those lines.
Unfortunately for Ryan Reynolds, despite his dialogue work, even he realized early on that the Wade Wilson in X-Men Origins: Wolverine was not the faithful iteration he had hoped to play. Wilson returned later in the story, but his mouth had been sewn shut and he'd been turned into Weapon XI, unofficially nicknamed "Barakapool." By that point, Reynolds was barely involved with playing the character. The actor continued:
If you watch the movie, I'm actually playing only a small section, and another actor, this gifted stunt performer, is doing the lion's share of that work. The conversation at the time was 'If you want to play Deadpool, this is your chance to introduce him. And if you don't want to introduce him in this fashion, we'll have someone else play him.'
Due to X-Men Origins: Wolverine's critical beating, as well as Deadpool's inherently weird tone, it wasn't until 2014 until the solo Deadpool movie was green-lit, and that was only because animated test footage leaked online was so well received by fans that Fox agreed to take the plunge. It paid off, and Ryan Reynolds was finally able to redeem the smart-ass mercenary following his disappoint cinematic debut, both on camera and helping out with the script.
Now Ryan Reynolds has found his niche as the legitimate Deadpool, fans can look forward to seeing him reprise the Merc with the Mouth when Deadpool 2 is released sometime in 2018.