Iron Man's Hulk Cameo is Part of a Bigger, Secret Story

Tony Stark has history with Thunderbolt Ross.
Robert Downey Jr.'s Tony Stark had a cool cameo in The Incredible Hulk - and tie-in comics provide the context.

Iron Man, Disney Fanon Wiki

IF Avengers: Secret Wars is as big of a crossover event as it's

She Hulk To Defend Tony Stark For Murder In New Invincible Iron Man?

Archive ScreenRant

Marvel's Kevin Feige Explains Robert Downey Jr.'s Return as Iron Man - Inside the Magic

Iron Man 2 (2010) - FAQ - IMDb

Was Tony Stark inside the Hulk Buster (Veronica) or was he

Archive ScreenRant

Iron Man, Marvel Cinematic Database

Bruce Banner (Earth-616), Marvel Database

Iron Man's 10 Most Clever Tech Upgrades Over His 11 Years In The MCU

Mark XLIV Iron Man Armor, Marvel Cinematic Universe Wiki