1. Mark Ruffalo is the third movie Hulk in the last 10 years.You thought Andrew Garfield quickly replacing Tobey Maguire as Spider-Man was bad? Just look at the film history of Dr. Bruce Banner, one of Marvel's most iconic characters who happens to turn into a big, burly green guy when he gets ticked off. Australian star Eric Bana crashed U.S. shores in 2003 in Ang Lee's "Hulk," and five years later Edward Norton picked him up in "The Incredible Hulk." Negotiations with Norton for "The Avengers" stalled, so in stepped Ruffalo, a veteran of quieter indie flicks like "You Can Count on Me" and "The Kids Are All Right." Will another actor play the Hulk in "Avengers 2"? With the character's track record, anything can happen.
2. Nifty voiceover work: the gruff, growling vocals of the Hulk were actually provided by an uncredited Lou Ferrigno, who played the green guy in 70s TV series "The Incredible Hulk" and beat up Jason Segel for calling him 'Hulk' in "I Love You, Man." Meanwhile, U.K. vet Paul Bettany ("A Beautiful Mind," "Priest") reprised his role as Jarvis, the computer program that helps Iron Man navigate through his tougher physical demands, as he did in "Iron Man" and its sequel.
3. Hemsworth Domination: 28-year-old Aussie Chris Hemsworth, who returned as Thor for "The Avengers" after headlining in his own comic book vehicle last year, just starred in the movie with the top-grossing opening weekend of 2012. And who was featured in the movie with the second-highest debut weekend of the year? None other than his 22-year-old brother, Liam Hemsworth, who played Gale Hawthorne in the big-screen adaptation of "The Hunger Games."