The screenwriters behind 'Deadpool & Wolverine' told 'IndieWire' that they pitched Robert Downey Jr. on cameoing as Iron Man for the movie's opening scene along with Jon Favreau's Happy Hogan, though they did not know the actor was in discussions to play Doctor Doom in the next 'Avengers' movie at the time.
https://people.com/robert-downey-iron-man-cameo-deadpool-wolverine-8693…