I'll play! Let's see ... How about The Avengers, Tony, illness. Maybe he's hiding it from the team because there's an important mission, or else he honestly thinks he's okay until Jarvis alerts him to his temperature. Something acute, please, like the flu or poisoning or magic fever ray of doom. I'd love delirious!Tony in real danger, whether in-suit or out, and the team, or your favorite member of the team, coming to the rescue.