EntertainmentMoviesAction MoviesMarvel MoviesAvengers: DoomsdayTom Holland was one of the first to know about Robert Downey Jr.’s Doctor Doom casting but says it was a “tough secret to sit on” because he has a “reputation for ruining things"When you purchase through links on our site, we may earn an affiliate commission.Here’s how it works. EntertainmentMoviesAction MoviesMarvel MoviesAvengers: DoomsdayTom Holland was one of the first to know about Robert Downey Jr.’s Doctor Doom casting but says it was a “tough secret to sit on” because he has a “reputation for ruining things"When you purchase through links on our site, we may earn an affiliate commission.Here’s how it works. When you purchase through links on our site, we may earn an affiliate commission.Here’s how it works. (Image credit: Columbia Pictures) Spider-Man actor Tom Holland was one of the first to know aboutRobert Downey Jr.’s shock return to the MCU as …