Al Pacino

As said, there was a time when appearing in comic book movies (others than focused on Batman) wasn't on the bucket list of the Hollywood's greats. However, times have changed and now we see stars like Michael Douglas and Sylvester Stallone joining the Marvel Cinematic Universe in roles that could span several movies.
One other star has expressed his interest in joining this shared universe, although he didn't say as whom "“ and this star is none other than Al Pacino, who made history with movies like The Godfather, Dogs Day Afternoon, Heat, and quite a few others.
After viewing Guardians of the Galaxy back in 2014, the actor praised the movie as being one of the most entertaining, inventive, and beautiful films he has ever since. As such, the actor also said afterwards that he has already met with Kevin Feige and that he has a role in an upcoming superhero flick.
Which is great!
