One ad libbed line in the first 'Iron Man' changed everything for Marvel

"I am Iron Man."
Robert Downey Jr.-as-Tony Stark utters that short sentence in the waning moments of 2008's Iron Man, the movie that kicked off the Marvel Cinematic Universe. In the fictional moment, Stark opted to cast aside prepared remarks that would have kept his secret identity safe and out himself instead.
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It's such a lightning strike moment for a movie based on comic books, where secret identities are oft