Downey was originally going to make a cameo appearance in Deadpool 3 as Iron Man but he turned it down because he wanted to play Doctor Doom

Recently, Deadpool and Wolverine screenwriters Rhett Reese and Paul Wernick were interviewed by foreign media and revealed that they originally wrote a scene for Robert Downey Jr. to play Iron Man again, but Downey refused to shoot. It was not until recently that they learned that Downey would return to Marvel to play Doctor Doom that they realized this was the real reason why Downey declined.

The film's co-writer said: "We didn't know about Doctor Doom at the time. Logically, it's impossible for a big star like him to play two roles in the MCU at the same time."

The two screenwriters revealed that "Deadpool" Ryan Reynolds "pressed" Downey Jr. before the filming began. After getting the other party's approval, the screenwriter wrote the scenes with the participation of Iron Man, and Downey also came to read the script. The crew did not know at the time that Downey was already negotiating with Marvel to play Doctor Doom.

In the original script of "Deadpool vs. Wolverine", 2018 Tony Stark and Happy appeared together to interview Deadpool, but in the final film, only Happy appeared.

The screenwriter of the film also had a vision: the six members of the original Avengers returned together to interview Deadpool, but rejected him, causing Deadpool to swear at every member of the Avengers.